The growth process of silver thin films deposited by pulsed laser ablation in a controlled inert gas atmosphere was investigated. A pure silver target was ablated in Ar atmosphere, at pressures ...ranging between 10 and 100
Pa, higher than usually adopted for thin film deposition, at different numbers of laser shots. All of the other experimental conditions such as the laser (KrF, wavelength 248
nm), the fluence of 2.0
J
cm
−2, the target to substrate distance of 35
mm, and the temperature (295
K) of the substrates were kept fixed. The morphological properties of the films were investigated by transmission and scanning electron microscopies (TEM, SEM). Film formation results from coalescence on the substrate of near-spherical silver clusters landing as isolated particles with size in the few nanometers range. From a visual inspection of TEM pictures of the films deposited under different conditions, well-separated stages of film growth are identified.
The surface of a detector grade CVD polycrystalline diamond sample (5×5×0.05mm3) was irradiated by an ArF excimer laser (λ=193nm, τ=20ns) to produce graphitic conductive layers.
In particular, two ...sets of four parallel graphitic strip-like contacts, with 1mm 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.
Hardness and reduced elastic modulus mappings of a graphitic strip induced by laser on diamond surface. Display omitted
•The manufacturing of strip-like graphitic contacts on diamond surface by laser-writing was carried out.•The contacts were created on diamond surface of both sides, with orthogonal orientation, to obtain a segmented all-carbon device capable to give bi-dimensional information during detection processes.•SEM and micro-Raman Spectroscopy analyzes allowed understanding the physical evolution of the graphitization process, and how the morphological and structural changes depend on laser processing.•Phenomena of chemical modifications were found by EDS: oxidation reactions were present on all the irradiated areas, with increasing intensity values for the most damaged zones.•Nano-indentation investigations were performed showing that hard-soft transformation occurred depending on the locally deposited energy and in agreement with the changes of hybridization (sp3→sp2) of carbon atoms.•Current-voltage analyses allowed to verify the ohmic behavior of the contacts and to evaluate the resistivity values of every strip, which range from 2.5 × 10-5 Ωm up to 3 × 10-5 Ωm.
► We produced gold nanoparticles using Pulsed Laser Deposition at different pressures. ► We have made the analysis of the light emission intensity profiles of the plume. ► Good performance of the ...substrates for SERS applications is reported.
Using UV pulses from KrF excimer laser, Au targets were ablated in varying pressures of argon to deposit Au nanoparticle (NP) arrays. The morphology of these films from island structures to isolated NPs, observed by SEM and TEM, depends on the gas pressure (10–100Pa) and pulse number keeping other deposition parameters constant. By fast imaging of the plasma with an iCCD camera at different time delays with respect to the arrival of the laser pulse, we study the plasma propagation regime and we measured its initial velocity. These data and the measured average ablated mass per pulse were introduced to the mixed propagation model to calculate the average asymptotic size of clusters grown in the plume which were compared with NP sizes from TEM measurements. UV–visible Spectroscopy revealed changes of surface plasmon resonance with respect to NP size and spatial density and distribution on the surface. Suitable wavelength to excite the localized surface plasmon was chosen to detect ultra-low concentrations of Rhodamine and Apomorphine as an application to biomedical sensors, using Surface Enhanced Raman Spectroscopy (SERS). A comparison of SERS spectra taken under identical conditions from commercial substrates and from PLD substrates show that the latter have superior performances.
Nanostructured gold thin films deposited by pulsed laser ablation show remarkable plasmonic properties and can be used as sensors based on surface-enhanced Raman scattering. The substrates are ...deposited onto
1
×
1
cm
2
inert supports and show a uniform morphology along that area. On the contrary, we observe a considerable dependence of the film surface morphology and plasmonic response on its position on the substrate holder. This is due to the high directionality of the species emitted in the ablation process. By keeping the substrate holder rotating in an off-axis configuration, a uniform film performance can be obtained, minimizing the differences in the plasmonic properties of the deposited films. A model of the geometry of the deposition set-up captures the details of the process and gives indications to improve the uniformity of the plasmonic properties from sample to sample. The SERS performance of the produced films was assessed with the new anti-epileptic drug perampanel.
In this work graphitic structures were fabricated on high quality polycrystalline CVD diamond by using a UV laser beam (λ=193nm). 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.
When a diamond graphitization process is induced, for example by excimer laser which irradiates the diamond surface, two phenomena occur: diamond graphititization and graphite ablation. The figure shows the physical evolution of the average height of the graphitic spots obtained after laser-diamond interaction, at laser fluence of 5J/cm2, with respect to the number of pulses. The measurements were obtained by AFM investigations (zero level refers flat unirradiated diamond surface). For one and two pulses it dominates a swelling phenomenon which represents the diamond graphitization process (the swelling is due to different mass density between diamond and graphite phases), while for four and eight pulses the graphite ablation dominates generating crates with increasing depth. Display omitted
•The physical evolution of the diamond graphitization process was studied.•The characterizations of graphitization and ablation processes of diamond were made by AFM and micro-Raman investigations.•The realization and optimization of ohmic graphitic contacts on diamond surface were done.•The response of full carbon detector to an ionizing particle and estimation of its CCE were reported.
An effective method for the production of surface enhanced Raman scattering (SERS) active substrates is presented. Nanostructured silver thin films are pulsed laser deposited in an argon atmosphere. ...The films consist of arrays of nanoparticles whose size is controlled by the Ar pressure. The surface morphology of the films can be tuned by the laser pulse number. Nanoparticle size is calculated by a phenomenological model taking into account the dynamics of the laser generated silver plasma. The SERS activity of the films is investigated by Raman scattering of adsorbed rhodamine 6G at different concentrations.
A phenomenological mixed-propagation model that describes the expansion of an ablation plume through a buffer gas is introduced. Selected experiments including LaMnO
3
and tin ablation in oxygen, as ...well as tungsten ablation in argon, are analysed. For given ablation conditions the expansion parameters required to model the growth of clusters in the expanding plasma plume are deduced and the average asymptotic size of the clusters is calculated and compared (for tungsten) with the size of clusters measured by transmission electron microscopy.
Surface-enhanced Raman scattering is a well-established technique for molecular detection at low concentration, which is becoming increasingly popular in the field of biotechnology and health ...sciences. Since the process is understood in depth, the technique is becoming reliable. In this contribution, we consider another aspect of SERS besides molecular detection, focusing on the binding mechanisms of a complex system such as a protein to the noble metal substrates required by the technique itself. We also show that using a solid nanostructured substrate produced by controlled pulsed laser deposition SERS enables label-free detection of a protein. This is checked on lysozyme as a well-known prototype. Use of solid substrates with controlled morphology proves advantageous over colloidal systems for SERS applications. Moreover, such substrates are superior in terms of shelf life, packaging and ease of shipment.
A mixed-propagation picture for the expansion of an ablation plume through a buffer gas at different pressures is proposed after a brief discussion of the available analytical expansion models. Using ...parameter values deduced by the model the size of carbon clusters formed during plume propagation in helium is evaluated and compared with experimental data. Starting from experiments on silver plume propagation through molecular oxygen the size of silver clusters is predicted.