Silica two-dimensional substrates and nanowires (NWs) forests have been successfully decorated with Au nanoparticles (NPs) through laser ablation by using a pulsed ArF excimer laser, for sensor applications. A uniform coverage of both substrate surfaces with NPs has been achieved controlling the number of laser pulses. The annealing of the as-deposited particles resulted in a uniform well-defined distribution of spherical NPs with an increased average diameter up to 25 nm. The deposited samples on silica NWs forest present a very good plasmonic resonance which resulted to be very sensitive to the changes of the environment (ethanol/water solutions with increasing concentration of ethanol) allowing the detection of changes on the second decimal digit of the refractive index, demonstrating its potentiality for further biosensing functionalities.

A full carbon diamond detector is proposed for the active target of PADME, an experiment which uses the positron beam of the BTF (Beam Test Facility) at the Laboratori Nazionali di Frascati to search for the production of dark photons in e+e - annihilation (M. Raggi et al., Adv. High Energy Phys. 2014 (2014) 959802). This paper presents the preliminary results of a beam test done in November 2015 of the PADME active target prototype. © CERN on behalf of the ATLAS and CMS Collaborations.

In this work graphitic structures were fabricated on high quality polycrystalline CVD diamond by using a UV laser beam (lambda = 193 nm). Two different kinds of structures were realized on diamond to study the evolution from diamond to graphite at different irradiation conditions (spot like structures) and to study their electrical transport properties (strip like structures). The graphitic structures were characterized structurally and morphologically by micro-Raman spectroscopy and atomic force microscopy. The electrical properties were evaluated using the transmission line model. Finally, a full carbon detector was built and tested showing good nuclear detection properties.

Abstract: Matrix-assisted pulsed laser evaporation (MAPLE) was used to deposit layers of poly(9,9-dioctylfluorene) (PFO) to study the relation between the solvent properties (laser light absorption, boiling temperature and solubility parameters) and the morphology of the deposited films. To this end, the polymer was diluted (0.5 wt%) in tetrahydrofuran—THF, toluene and toluene/hexane mixtures. The thickness of the films was equal to 70 ± 20 nm. The morphology and uniformity of the films was investigated by Atomic Force Microscopy and by the photoluminescence emission properties of the polymer films, respectively. It is shown that, although the solubility parameters of the solvents are important in controlling the film roughness and morphology, the optical absorption properties and boiling temperature play a very important role, too. In fact, for matrices characterized by the same total solubility parameter, lower roughness values are obtained for films prepared using solvents with lower penetration depth of the laser radiation and higher boiling temperatures.

Thin films of chromium oxides were deposited on Si substrates by KrF laser ablation of a chromium target in O(2) atmosphere (0.05-5.0 Pa). Films exhibit semiconducting properties with band gap increasing (0.32-0.71 eV) with increasing pressure from 0.05 to 1.0 Pa. The largest values of the thermoelectromotive force coefficient S (similar to 3.5-4.5 mV/K) were measured in the temperature range 270-290 K for the film deposited at 1.0 Pa. The S coefficient decreases in the same temperature range for the film deposited at lower oxygen pressures.

The surface of a detector grade CVD polycrystalline diamond sample (5 × 5 × 0.05 mm3) was irradiated by an ArF excimer laser (λ = 193 nm, τ = 20 ns) to produce graphitic conductive layers. In particular, two sets of four parallel graphitic strip-like contacts, with 1 mm pitch, were created along the whole sample on the top and on the rear surfaces of the sample respectively. The two series of stripes lie normally to each other. Such a grid allows to obtain a segmented all-carbon device capable of giving bi-dimensional information on particle detection processes in nuclear applications. Afterwards, an extensive characterization of the samples was performed: SEM and micro-Raman investigations to study the morphological and structural evolution of the irradiated areas, EDS measurements to individuate any absorption phenomena from environment associated to laser treatment, and nanoindentation mapping to understand how the hard-soft transformation occurred depending on the locally transferred energy. Finally, current-voltage analyses were carried out checking the ohmic behavior of the diamond-graphite contact. By comparing the results of the different characterization analyses, a strong periodicity of the modified surface properties was found, confirming the reliability and reproducibility of the laser-induced graphitization process. The results demonstrate that the laser-writing technique is a good and fast solution to produce graphitic contacts on diamond surface and therefore represents a promising way to fabricate segmented all-carbon devices.

In the last years there has been an increase of interest in diamond devices because of the promising applications in different field, such as high-energy physics, radiotherapy and biochemical applications. In particular, a new frontier is represented by the realization of full-carbon detectors characterized by graphite electrodes, which give to the devices considerable advantages like high radiation hardness, perfect mechanical adhesion and good charge collection properties. In this paper the manufacturing of full-carbon devices and their detection performances are illustrated and compared to a reference diamond detector characterized by traditional electrodes.

We report on the first dielectric investigation of high-k yttrium copper titanate thin films, which were demonstrated to be very promising for nanoelectronics applications. The dielectric constant of these films is found to vary from 100 down to 24 (at 100 kHz) as a function of deposition conditions, namely oxygen pressure and film thickness. The physical origin of such variation was investigated in the framework of universal dielectric response and Cole–Cole relations and by means of voltage dependence studies of the dielectric constant. Surface-related effects and charge hopping polarization processes, strictly dependent on the film microstructure, are suggested to be mainly responsible for the observed dielectric response. In particular, the bulky behaviour of thick films deposited at lower oxygen pressure evolves towards a more complex and electrically heterogeneous structure when either the thickness decreases down to 50 nmor the films are grown under high oxygen pressure.

In this study, we examine at both experimental and fundamental levels, the experimental evidence of nanoparticle formation in transmission electron microscopy (TEM) metal grids annealed at temperatures lower than the melting point of the corresponding metal bulk material. Our experimental investigation considers the most thermally unstable TEM grids (i.e. Cu-grids) and inspects the possible sources and mechanisms of contamination of thin films, conventionally deposited on carbon-coated Cu-grids. The investigations are supported by morphological–compositional analyses performed in different regions of the TEM sample. Then, a general model is formulated and discussed in order to explain the grid thermal instability, based on the critical role of edge-melting (i.e. melting initiated at edges and corners of th egrid bars), the enhanced rate of evaporation from a liquid surface and the polycristallinity of the grid bars.Hence, we totally disregard conventional arguments such as bulk evaporation and metal vapor pressure and, in order to emphasize and clarify the alternative point of view of our model, we also overview the nano-scale melting phenomenology relevant to our discussion and survey the discrepancies reported in the literature.

In this paper we report on the effects of the insertion of Cr atoms on the electrical and optical properties of indium tin oxide (ITO) films to be used as electrodes in spinpolarized light-emitting devices. ITO films and ITO(80 nm)/Cr-doped ITO(20 nm) bilayers and Cr-doped ITO films with a thickness of 20 nm were grown by pulsed ArF excimer laser deposition. The optical, structural, morphological wand electrical properties of ITO films and ITO/Cr-doped structures were characterized by UV-Visible transmission and reflection spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM) and Hall-effect analysis. For the different investigations, the samples were deposited on different substrates like silica and carbon coated Cu grids. ITO films with a thickness of 100 nm, a resistivity as low as similar to 4 x 10(-4) Omega cm, an energy gap of similar to 4.3 eV and an atomic scale roughness were deposited at room temperature without any post-deposition process. The insertion of Cr into the ITO matrix in the upper 20 nm of the ITO matrix induced variations in the physical properties of the structure like an increase of average roughness (similar to 0.4-0.5 nm) and resistivity (up to similar to 8x10(-4) Omega cm). These variations were correlated to the microstructure of the Cr-doped ITO films with particular attention to the upper 20 nm.

Brookite titanium dioxide (TiO2) nanorods, synthesized by a surfactant-assisted aminolysis route, were used as precursors for the fabrication of thin films by using the matrix-assisted pulsed-laser deposition (MAPLE) technique. Thin films with controllable thickness were grown on a variety of substrates for different characterizations. High-resolution scanning and transmission electron microscopy investigations evidenced the formation of rough TiO2 films incorporating individually distinguishable nanocrystals with different shapes. Suitable alumina substrates equipped with interdigitated electrical contacts (IDC) and heating elements were used to fabricate gas-sensing devices based on resistive transduction mechanism. Electrical characterization measurements in controlled environment were carried out. Typical gas sensor parameters (such as gas response, sensitivity, stability and detection limit) towards selected oxidizing and reducing gases, namely NO2 and CO, respectively, were extracted in dark condition. Very interesting optically activated enhancement of the response towards NO2 oxidizing gas was achieved in controlled atmosphere upon irradiating the sensing layer with UV light with low energy close to the TiO2 sensing layer band-gap width.

In this work, we have studied the structure and the morphology of a graphite layer induced on the surface of a polycrystalline thermal grade CVD diamond by focusing a pulsed excimer laser operating at KrF (wavelength 248 nm) and ArF (wavelength 193 nm) mixtures. By micro-Raman and photoluminescence spectroscopies, as well as scanning electron microscopy, we reported the synthesis of a turbostratic t-graphite layer after irradiation with ArF laser. By contrast, irradiating with a KrF laser beam, we obtained a disordered graphite layer with 10 laser shots, while 200 consecutive laser pulses resulted in target ablation.

Titanium dioxide (TiO2) nanorods in the brookite phase, with average dimensions of 3–4 nm × 20–50 nm, were synthesized by a wet-chemical aminolysis route and used as precursors for thin films that were deposited by the matrix-assisted pulsed laser evaporation (MAPLE) technique. A nanorod solution in toluene (0.016 wt% TiO2) was frozen at the liquid-nitrogen temperature and irradiated with a KrF excimer laser at a fluence of 350 mJ/cm2 and repetition rate of 10 Hz. Single-crystal Si wafers, silica slides, carbon-coated Cu grids and alumina interdigitated slabs were used as substrates to allow performing different characterizations. Films fabricated with 6000 laser pulses had an average thickness of ∼150 nm, and a complete coverage of the selected substrate as achieved. High-resolution scanning and transmission electron microscopy investigations evidenced the formation of quite rough films incorporating individually distinguishable TiO2 nanorods and crystalline spherical nanoparticles with an average diameter of ∼13 nm. Spectrophotometric analysis showed high transparency through the UV-Vis spectral range. Promising resistive sensing responses to 1 ppm of NO2 mixed in dry air were obtained.

Nearly amorphous high-k yttrium copper titanate thin films deposited by laser ablation were investigated in both metal-oxide-semiconductor (MOS) and metal-insulator-metal (MIM) junctions in order to assess the potentialities of this material as a gate oxide. The trend of dielectric parameters with film deposition shows a wide tunability for the dielectric constant and AC conductivity, with a remarkably high dielectric constant value of up to 95 for the thick films and conductivity as low as 6 x 10(-10) S cm(-1) for the thin films deposited at high oxygen pressure. The AC conductivity analysis points out a decrease in the conductivity, indicating the formation of a blocking interface layer, probably due to partial oxidation of the thin films during cool-down in an oxygen atmosphere. Topography and surface potential characterizations highlight differences in the thin film microstructure as a function of the deposition conditions; these differences seem to affect their electrical properties.

Among spintronic materials, mixed-valence manganite La(0.7)Sr(0.3)MnO(3) (LSMO) is widely investigated due to its half-metal nature. LSMO thin films were grown by pulsed laser deposition (PLD) onto amorphous silica substrates heated at nearly 600 degrees C. An ArF excimer laser was chosen to induce ablation due to its more energetic photons compared to the other quoted excimer laser sources. Different oxygen pressures were considered in order to study the influence of oxygen on the LSMO optical and electrical properties. In this respect, the visible transparency percentage of the deposited films is found good enough for spin-OLED applications. The absorption coefficient shows an absorption band tunable as a function of the oxygen content. Its energetic location and evolution with the oxygen content demonstrate it originates from radiative transitions between the spin-majority bands separated by the Jahn-Teller distortion. All of this lets relate the deposition oxygen pressure to the Mn(3+) ion content in each film and interpret electrical data. The 200 and 100 nm thick samples exhibit weak metallic transport behavior at room temperature with a resistivity of 4.8 and 6.9 Omega cm, respectively. Concerning the resistivity response versus temperature, the measured low metal-insulator transition temperature (150 K) is related to the sample structural features as involved by the depositions. Two different transport mechanisms describe the conductivity regime of the deposited samples, namely the small polaron variable range hopping (VRH) and the Arrhenius law.

We created a radiation detection device from a plate of high quality polycrystalline CVD diamond, fabricating nano-graphite electrical contacts on both diamond surfaces, by front and back irradiation with a 193 nm ArF excimer laser. We measured the electrode electrical resistance and evaluated a graphite resistivity of about 10−5 Ω ⋅ m. The ohmic nature of the contact graphite/diamond is established measuring the current–voltage characteristic that it is described by a linear behavior up to 90 V, by a Space Charge Limited (SCL) regime above 100 V and below 300 V, and by a Trap Filled Space Charge Limited (TFSCL) regime above 300 V. Finally, we investigated the device response in counting mode to a 60Co γ-rays source and to a 120 GeV proton beam proving its capability to work as a fast nuclear radiation detector.

Ferromagnetic materials exhibiting at room temperature combination of good conductivity, magnetic and opto-electronic properties are needed for the development of functional spin-devices. Mixed-valence LSMO is an optimal source of fully spin-polarized carriers and shows a rich physics of magnetic phases and transport mechanisms. Many factors, such as growth temperature, oxygen stoichiometry, temperature-dependent oxygen desorption rate, structural matching between the growing film and substrate, film thickness, and defects, influence the LSMO properties. Stabilization of ferromagnetic and conductive behaviours is linked to structural order. Therefore a growth approach allowing congruent deposition of complex materials under controlled, reproducible and tunable conditions is strongly needed. In this respect pulsed laser deposition reveals a well-suited choice. This review aims to give an overview on LSMO thin film properties, deposition and applications, especially in the emerging organic spintronics.

The matrix-assisted pulsed laser evaporation (MAPLE) has been recently exploited for depositing films of nanomaterials by combining the advantages of colloidal inorganic nanoparticles and laser-based techniques. MAPLE-deposition of nanomaterials meeting applicative purposes demands their peculiar properties to be taken into account while planning depositions to guarantee a congruent transfer (in terms of crystal structure and geometric features) and explain the deposition outcome. In particular, since nanofluids can enhance thermal conductivity with respect to conventional fluids, laser-induced heating can induce different ablation thermal regimes as compared to the MAPLE-treatment of soft materials. Moreover, nanoparticles exhibit lower melting temperatures and can experience pre-melting phenomena as compared to their bulk counterparts, which could easily induce shape and or crystal phase modification of the material to be deposited even at very low fluences. In this complex scenario, this review paper focuses on examples of MAPLE-depositions of size and shape controlled nanoparticles for different applications highlights advantages and challenges of the MAPLE-technique. The influence of the deposition parameters on the physical mechanisms which govern the deposition process is discussed.

The Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique is emerging as an alternative route to the conventional methods for depositing organic materials, although the MAPLE-deposited films very often present high surface roughness and characteristic morphological features. Films of the blue-emitting polymer, poly(9,9-dioctylfluorene)—PFO, have been deposited by MAPLE to investigate the influence of the laser fluence and repetition rate on both their topography and emission properties. The laser fluence has been changed from 150 up to 450 mJ/cm2 , while laser repetition rates of 2 and 10 Hz have been considered. The interplay/relationship between the topography and the emission properties of the MAPLE-deposited films has been studied by confocal microscopy, photoluminescence spectrometry and atomic force microscopy. It has been found that under high irradiation (fluence of 450 mJ/cm2) conditions, the sample surface is characterized by bubbles presenting the intrinsic PFO blue emission. Instead, while improvements in the film morphology can be observed for lowered fluence and laser repetition rate, green emission becomes predominant in such conditions. Such result is very interesting to better understand the MAPLE ablation mechanism, which is discussed in this study.

TiO2 nanorods in the brookite phase, having a mean size of 5 nm×50 nm, were prepared through a chemical route. The nanorods were dissolved in pure to luene (0,016 wt % TiO2). The solution was frozen at the liquid-nitrogen temperature and used as a target for the matrix-assisted pulsed laser evaporation (MAPLE) process. Target irradiation was accomplished with a KrF excimer laser (λ=248 nm,τ=20 ns), operated at fluences from F=25 to 350 mJ/cm2. Films were deposited at the repetition rate of 10 Hz using 6000 laser pulses. Film thickness resulted to be ∼ 100 nm at the highest fluence. It was not possible to use a higher number of laser pulses due to the melting of the target (~ 5 mm thick with a diameter of ~ 2.5 mm), even if continuously refrigerated at the LN temperature. Several substrates were used to fully characterize the deposited layers: <100> single-crystal Si wafers, silica slides, Cu carbon-coated grids and alumina interdigital slabs. High-resolution scanning and transmission electron microscopy investigations evidenced the formation of quite rough films incorporating individually distinguishable TiO2 single nanorods. Crystalline spheres were also detected in films, starting from the threshold fluence of 50 mJ/cm2 . Surface density and dimension of the spheres increase with increasing laser fluence. The sphere formation process and the target melting are discussed and attributed to nanosize effects. Films were positively tested as resistive sensors towards very low NO2 concentrations (≅ 1 ppm).

The formation of Pd nanoparticles (NPs) by matrix-assisted pulsed laser evaporation (MAPLE) of a palladium acetate solution has been studied as a function of the carrier solvent, laser-pulse number, metal precursor concentration and post-deposition thermal heating. Structural and compositional analyses demonstrate that: (i) the conventional MAPLE process can induce self-reduction of the metal salt precursor, thereby leading to the formation of metallic Pd(0) NPs; (ii) the solvent critically determines the size, morphology, and size distribution of the resulting NPs; and (iii) the cumulative effects of laser-pulse number and solute concentration are less influential than the type of solvent used. For diethyl ether-derived samples, a bimodal distribution of NP sizes spanning from ∼1 nm up to 20 nm was obtained. Conversely, by using acetone, a mono-modal distribution of sizes in the ∼1 nm–6 nm range (mean diameter of 1.5±0.7 nm) and a more uniform and densepacked surface coverage (NP coverage was twice as dense as the one obtained with diethyl ether) resulted in. These observations point out that solvents with low dynamical viscosity coefficients and high volatility favor the formation of larger and more broadly dispersed NPs. A general theoretical picture has been proposed to describe the NP formation pathways on account of the solvent properties and the mechanisms underlying the MAPLE process enabled by the technique.

The promising results obtained with the MAPLE-deposition of nanostructured thin films, to be used in different fields, are reviewed. Nanoparticles (TiO2, SnO2, CdS) and nanorods (TiO2) with well defined dimensions were suspended in appropriate solvents (distilled water, toluene) with low concentration (1wt% or less). The solutions were flash frozen at the liquid nitrogen temperature to form the targets to be laser irradiated. The MAPLE process allowed a successful transfer from the target to rough and flat substrates, preserving the starting composition and crystalline phase of the nanostructures in a wide range of experimental conditions. In contrast, a careful choice of the laser fluence is mandatory to avoid shape modifications. Growth of metal nanoparticles with a low dispersion in size was also obtained by the MAPLE technique, starting from target solutions of a metallorganic element (AcPd) diluted in different solvents (acetone, diethyl ether). It seems that selecting the solvent with appropriate values of viscosity and boiling temperatures, it is possible to modulate the nanoparticles size. Most of the deposited nanostructured films were tested as sensing elements for gas sensors.

Metal oxide sensors with active Fe2O3 and CoFe2O4 nanoparticle arrays were studied. Sensing nanoparticle films from 1, 2, 4 or 7 monolayers were deposited by Langmuir-Blodgett technique. Sensors are formed on the alumina substrates equipped with heating meander. Langmuir-Blodgett layers were heated or UV irradiated to remove the insulating surfactant. Sensing properties were studied towards CO or NO2 gases in concentrations between 0.5 and 100 ppm in mixture with the dry air. Best response values Igas/Iair were obtained with CoFe2O4 device being 3 for 100 ppm of CO and with Fe2O3 device being (38)-1 for 0.5 ppm of NO2.

We investigate the optical properties of ITO and Cr-doped ITO films deposited at room temperature by pulsed laser deposition onto amorphous SiO2 substrates. Our analysis approach is based on the Tauc's plot method applied to the absorption coefficient estimated by a route realistically describing the film structural features and including the contribution of the non-measurable film–substrate interface. Going beyond the conventional application of the Tauc's plot method, we quote two different transition energies for ITO and Cr-doped ITO and discuss their origin in the framework of a band-structure picture as a function of film thickness, Cr changes of the host ITO dispersion and Cr-doping content. In contrast to the conventional optical ITO description, we account for the existence of direct dipole forbidden transitions between the ITO fundamental band edges, involving different electronic and optical band gaps. Our results and discussion demonstrate that disregarding this theoretically established picture, as occurs in the experimental literature, would lead to conclusions inconsistent with the Cr-induced band occupation and effects on ITO dispersions. Preliminary optical (based on transmittance and reflectance spectra as well as band-tailing effects), electrical and structural inspection of the samples are also considered to check reliability and consistency of our discussion.

We report on nitrogen dioxide (NO(2)) sensing measurements by means of zinc oxide films presenting different morphologies. The variation in the photoluminescence emission of the films is employed as transduction mechanism to detect the presence of NO(2) gas molecules at room temperature. The significant role of film morphology on the sensing properties is presented and possible limits in the use of ZnO nanostructures for NO(2) detection at high gas concentration (>20 ppm) and low gas flow (50 ml/min), where a worsening of the sensor response is observed, are discussed. These features are ascribed to a likely incomplete reversibility of the NO(2) adsorption process and examined in connection with the mechanisms of interaction between NO(2) molecules and ZnO.

The optical response of 200 nm thick La0.7Sr0.3MnO(3 − δ) films, deposited by pulsed laser deposition on amorphous silica substrates heated at nearly 600 °C, under different oxygen pressures (0.1 Pa, 0.5 Pa, 1 Pa, 5 Pa and 10 Pa), is reported. The effects of the oxygen non-stoichiometry are investigated at room temperature dealing with the absorption coefficient and the Tauc's plotmethod rather than conventional optical conductivity. The absorption curves are evaluated by an algorithm able to realistically describe the behavior of thin films without exploiting numerical extrapolations or simplified theoretical models or ab-initio calculations. Optical features, tunable by the growth oxygen pressure, are discussed based on the known theoretical and experimental scenario

A poly-(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C-61-butyric-acid-methyl-ester (PCBM) bilayer structure has been realized by single step matrix-assisted pulsed laser evaporation (ss-MAPLE) technique using the same solvent for both the polymers under vacuum conditions. Our ss-MAPLE procedure allows the fabrication of polymeric multilayer device stacks, which are very difficult to realize with the conventional solvent assisted deposition methods. A proof of concept bilayer P3HT/PCBM solar cell based on ss-MAPLE deposition has been realized and characterized. This demonstration qualifies ss-MAPLE as a general and alternative technique for the implementation of polymeric materials in hetero-structure device technology.

A highly dense and uniform layer of Au nanoparticles (NPs) on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film has been produced by the pulsed laser deposition (PLD) technique toward the production of an improved efficiency photovoltaic device. The advantage of PLD over other techniques is the easy and precise control of the Au NPs size and spatial distribution, without needing of further NP surface functionalization. The efficiency enhancement factor related to Au NPs doping has been evaluated in a solar cell based on poly-(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) diffused bilayer. The short-circuit current density, J SC, increases by 18 % and the power conversion efficiency by 22 %, respectively, in comparison with an equivalent device without Au NPs. The optical and morphological properties of the Au NPs layer have been selected in order to evaluate the contribution of the surface plasmon resonance as enhancement factor of the solar cell efficiency, in a range size where light scattering is negligible.

The state of the art of Chemical Vapor Deposition (CVD) diamond detector technology is reviewed and its applications in several fields, such as highenergy physics, radiotherapy and nuclear fusion reactors, are described. The impact of the newest front-end electronics design is discussed. Finally, recent innovative developments using laser techniques are also illustrated together with very recent results.

We irradiated two diamond detectors with 62 MeV energy proton beam up to an integrated fluence of about 10$^{16}$protons/cm$^{2}$ at INFN-LNS in Catania (Italy). The detectors were made by two high purity poly-crystal diamond sensors. The electric contacts of the two diamond sensors were from different sources and made with different techniques: a proprietary DLC/Pt/Au electric contact and our own novel UV Laser technique. We measured the detector pulse height before and after irradiation using the same proton beam with reduced intensity. The radiation damage was than quantified in terms of charge collection distance as measured with a beta source. Finally, the degradation of the global detector time performance due to the reduced signal was evaluated comparing the time dispersion between the two detectors placed on the beam before and after irradiation.

In this work we show preliminary results of radiation damage for a polycrystalline diamond with graphite contacts in terms of time response after 62 MeV protons irradiation for a total fluence of (2.0±0.08)×1015 protons/cm2. In addition, we describe the realization of a new type of device made with graphite micro-strips by laser micro-writing on diamond surface. In this way we made 20 graphite micro-strips of width about 87 m and spacing between each other of about 60 m.

A spectrophotometric strategy, termed multilayer-method (ML-method), is presented and discussed to realistically calculate the absorption coefficient of each individual layer embedded in multilayer architectures without reverse engineering, numerical refinements and assumptions about the layer homogeneity and thickness. The strategy extends in a non-straightforward way a consolidated route, already published by the authors and here termed basic-method, able to accurately characterize an absorbing film covering transparent substrates. The ML-method inherently accounts for non-measurable contribution of the interfaces (including multiple reflections), describes the specific film structure as determined by the multilayer architecture and used deposition approach and parameters, exploits simple mathematics, and has wide range of applicability (high-to-weak absorption regions, thick-to-ultrathin films). Reliability tests are performed on films and multilayers based on a well-known material (indium tin oxide) by deliberately changing the film structural quality through doping, thickness-tuning and underlying supporting-film. Results are found consistent with information obtained by standard (optical and structural) analysis, the basic-method and band gap values reported in the literature. The discussed example-applications demonstrate the ability of the ML-method to overcome the drawbacks commonly limiting an accurate description of multilayer architectures.

Both a theoretical algorithm and an experimental procedure are discussed of a new route to determine the absorption/scattering properties of thin films deposited on transparent substrates. Notably, the non-measurable contribution of the film–substrate interface is inherently accounted for. While the experimental procedure exploits only measurable spectra combined according to a very simple algorithm, the theoretical derivation does not require numerical handling of the acquired spectra or any assumption on the film homogeneity and substrate thickness. The film absorption response is estimated by subtracting the measured absorption spectrum of the bare substrate from that of the film on the substrate structure but in a non-straightforward way. In fact, an assumption about the absorption profile of the overall structure is introduced and a corrective factor accounting for the relative film-to-substrate thickness. The method is tested on films of a well known material (ITO) as a function of the film structural quality and influence of the film–substrate interface, both deliberately changed by thickness tuning and doping. Results are found fully consistent with information obtained by standard optical analysis and band gap values reported in the literature. Additionally, comparison with a conventional method demonstrates that our route is generally more accurate even if particularly suited for very thin films.

A spectrophotometric strategy is presented and discussed for calculating realistically the reflectance spectrum of an absorbing film deposited over a thick transparent or semi-transparent substrate. The developed route exploits simple mathematics, has wide range of applicability (high-to-weak absorption regions and thick-to-ultrathin films), rules out numerical and curve-fitting procedures as well as model-functions, inherently accounts for the non-measurable contribution of the film-substrate interface as well as substrate backside, and describes the film reflectance spectrum as determined by the experimental situation (deposition approach and parameters). The reliability of the method is tested on films of a well-known material (indium tin oxide) by deliberately changing film thickness and structural quality through doping. Results are found consistent with usual information yielded by reflectance, its inherent relationship with scattering processes and contributions to the measured total reflectance.

This work deals with the realization and characterization of integrated graphitic contacts on diamond by means of laser irradiation (graphitization), in order to obtain good quality ohmic electrodes for nuclear radiation detectors to be used in high energy physics experiments. Unlike the conventional method used for the electrode production, which requires numerous steps and very well controlled environmental conditions, this alternative technique presents many advantages: the contacts are realized in air at room temperature in a single step. In this study, the characteristics of several graphitic structures realized on a diamond surface by changing the radiation-matter interaction parameters have been evaluated in order to define the best experimental conditions to create graphitic electrodes with low resistivity. The obtained results are promising: contacts perfectly adherent, with good charge collection properties, stable and resistant to ionizing radiation

To study the role of the solvent and of the laser fluence in the matrix-assisted pulsed laser evaporation (MAPLE) process, we used a soft polymer (polydimethylsiloxane— PDMS) as ‘‘sensing surface’’ and toluene as solvent. Thin films of the PDMS polymer were placed in the position of the growing film, while a frozen toluene target was irradiated with an ArF laser at the conventional fluences used in MAPLE depositions (60–250 mJ/cm2). Apart the absence of solute, the MAPLE typical experimental conditions for the deposition of thin organic layers were tested. The effects on the PDMS films of the toluene target ablation, at different fluences, were studied using atomic force microscopy and contact angles measurements. The results were compared with the effects produced on similar PDMS films by four different treatments (exposure to a drop of the solvent, to saturated toluene vapors and to plasma sources of two different powers). From this comparative study, it appears that depending on the MAPLE experimental conditions: (1) the MAPLE process may be ‘‘semidry’’ rather than purely dry (namely the solvent is likely to be present in the deposition environment near the growing film), (2) the solvent, if sufficiently volatile, is in form of vapor molecules (neutral, ionized and probably dissociated) rather than in liquid phase near the substrate and (3) at relatively high laser fluences ([150 mJ/cm2), the formation of an intense plasma plume results which can damage/affect a soft substrate as well as a growing polymer film.

In this paper we report on the growth and structural characterization of very thin (20 nm) Cr-doped ITO films, deposited at room temperature by double-target pulsed laser ablation on amorphous silica substrates. The role of Cr atoms in the ITO matrix is carefully investigated with increasing doping content by transmission electron microscopy (TEM). Selected-area electron diffraction, conventional bright field and dark field as well as high-resolution TEM analyses, and energy dispersive x-ray spectroscopy demonstrate that (i) crystallization features occur despite the low growth temperature and small thickness, (ii) no chromium or chromium oxide secondary phases are detectable, regardless of the film doping levels, (iii) the films crystallize as crystalline flakes forming large-angle grain boundaries; (iv) the observed flakes consist of crystalline planes with local bending of the crystal lattice. Thickness and compositional information about the films are obtained by Rutherford back-scattering spectrometry. Results are discussed by considering the combined effects of growth temperature, smaller ionic radius of the Cr cation compared with the trivalent In ion, doping level, film thickness, the double-target doping technique and peculiarities of the pulsed laser deposition method.

Chemically synthesized brookite titanium dioxide (TiO2) nanorods with average diameter and length dimensions of 3–4 nm and 35–50 nm, respectively, were deposited by the matrix-assisted pulsed laser evaporation technique. A toluene nanorod solution was frozen at the liquid-nitrogen temperature and irradiated with a KrF excimer laser (λ=248 nm, τ=20 ns) at the repetition rate of 10 Hz, at different fluences (25 to 350 mJ/cm2). The deposited films were structurally characterized by high-resolution scanning and transmission electron microscopy. 〈100〉 single-crystal Si wafers and carbon-coated Cu grids were used as substrates. Structural analyses evidenced the occurrence of brookite-phase crystalline nanospheres coexisting with individually distinguishable TiO2 nanorods in the films deposited at fluences varying from 50 to 350 mJ/cm2. Nanostructured TiO2 films comprising only nanorods were deposited by lowering the laser fluence to 25 mJ/cm2. The observed shape and phase transitions of the nanorods are discussed taking into account the laser-induced heating effects, reduced melting temperature and size-dependent thermodynamic stability of nanoscale TiO2.

The sensing performance comparisons presented in this work were carried out by exploiting a suitable magneto-plasmonic sensor in both the traditional surface plasmon resonance configuration and the innovative magneto-optic surface plasmon resonance one. The particular multilayer transducer was functionalized with TiO2 Brookite nanorods layers deposited by matrix assisted pulsed laser evaporation, and its sensing capabilities were monitored in a controlled atmosphere towards different concentrations of volatile organic compounds mixed in dry air.

The matrix assisted pulsed laser evaporation (MAPLE) technique is emerging as an alternative route to conventional deposition methods of organic materials (solution-phase and thermal evaporation approaches). However, the high surface roughness of the films deposited by MAPLE makes this technique not compatible with applications in electronics and photonics. In this paper we report the deposition of MAPLE-films of a green light emitting polymer, commercially named ADS125GE, with remarkable low roughness values, down to about 10 nm at the thickness conventionally used in photonic devices (similar to 40 nm). This issue is discussed as a function of polymer concentration, target-substrate distance and substrate rotation based on AFM topography images, roughness estimation and optical (absorption and luminescent) measurements. In addition we have fabricated an organic light emitting diode with this technique using the best deposition parameters which guarantee the lowest roughness. These results open the way to MAPLE applications in organic photonics and opto-electronics.

The development of alternative deposition techniques of conjugated polymeric compounds is an important step towards the fabrication of low cost multi-layered organic light emitting diodes suitable for display or lighting applications. In this work we show a white light -emitting polymeric hetero-structured diode consisting of three-stacked blue, red and green light emitting polymers. In order to circumvent the issue of selecting orthogonal solvents in solution -deposition approaches, we combine spin-coating with the Matrix Assisted Pulsed Laser Evaporation technique, resulting in the realization of a polymeric multilayered stack. By controlling the carriers and the energy transfer across the three light emitting layers interfaces, as well as the interplay between the deposition parameters, a pure white colour emission with Commission Internationale de l'Éclairage coordinates (X=0.327, Y=0.374) and a Color Rendering Index of 70 have been achieved. Our study represents the first proof of a light emitting diode made by multilayer polymeric thin films emitting white light.

Various kinds of zinc oxide (ZnO) nanostructures, such as columns, pencils, hexagonal pyramids, hexagonal hierarchical structures, as well as smooth and rough films, were grown by pulsed laser deposition using KrF and ArF excimer lasers, without use of any catalyst. ZnO films were deposited at substrate temperatures from 500 to 700°C and oxygen background pressures of 1, 5, 50, and 100 Pa. Quite different morphologies of the deposited films were observed using scanning electron microscopy when different laser wavelengths (248 or 193 nm) were used to ablate the bulk ZnO target. Photoluminescence studies were performed at different temperatures (down to 7 K). The gas sensing properties of the different nanostructures were tested against low concentrations of NO 2. The variation in the photoluminescence emission of the films when exposed to NO 2 was used as transduction mechanism to reveal the presence of the gas. The nanostructured films with higher surface-to-volume ratio and higher total surface available for gas adsorption presented higher responses, detecting NO 2 concentrations down to 3 ppm at room temperature