Amorphous As2S3 Films Research Articles

Femtosecond laser induced damage threshold incubation and oxidation in AS2S3 and AS2Se3 thin films

Laser surface structuring has emerged as a versatile technology for precise and localized material processing. When dealing with femtosecond lasers, thermal effects and collateral damage are reduced due to nonlinear light-matter interaction, improving the processing. This study explores the fabrication of microstructures using femtosecond pulses on thin films of chalcogenide glasses, which can be used for photonics applications, such as waveguides, fiber lasers, and photonic crystals. Moreover, the photoinduced changes in chalcogenide glasses have opened up new possibilities in optoelectronics, data storage, and other applications. Femtosecond laser machining of amorphous thin films of As2S3 and As2Se3 using femtosecond laser pulses is investigated through various microscopy techniques and spectroscopy tools, focusing on the impact of incubation effects and controlled photo-oxidation. This research contributes to a deeper understanding of the interaction of ultrafast pulses with chalcogenide glasses, promoting further advancements in photonics and optoelectronic applications.

Mass transport in amorphous As2S3 films due to directional light scattering under illumination by an oblique tightly focused beam

Photoinduced deformation of an amorphous As2S3 film surface under illumination by sub-bandgap (638 nm) and above-bandgap (532 nm) polarized laser light at oblique incidence are studied by atomic force microscopy performed directly after the film exposure to the laser beam. Photoinduced expansion as well as directional mass transport from the laser spot are observed. The photodeformation character under sub-bandgap and above-bandgap illumination are discussed in view of the optical forces (gradient force and scattering force) due to the interaction of light with the amorphous As2S3 film .

Hydrocarbons detection using surface plasmon resonance with As2S3 thin film waveguide

Surface plasmon resonance containing amorphous As2S3 film is proposed as a chemical sensor to highlight several liquid hydrocarbons. Method is label-free and is based on detection of small changes in the refractive index. As2S3 operates as plasmonic waveguide which confines the probing beam to the interface with liquid hydrocarbons. The method can easily distinguish hydrocarbons with very close refractive indices. The film thicknesses were optimized to obtain the best sensitivity and resolving power. Minimum reflectance of SPR less than 1 % was found for optimal calculated film thicknesses, the sensitivity to the refractive index changes being 2·10-5 .

Structural and optical study of Zn-doped As2Se3 thin films: Evidence for photoinduced formation of ZnSe nanocrystallites

Amorphous Zn-doped As2Se3 films with a nominal zinc content x up to 10 at.% were prepared by thermal evaporation. Their structure is characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoemission spectroscopy (XPS), and Raman spectroscopy. The AFM data show a considerable increase of the film surface roughness for films with x > 5 at.%. A strong gradient of the Zn content decreasing into the film depth is confirmed by the EDX and XPS data. Heavily Zn-doped (above 7 at.%) As2Se3 films reveal photostructural changes in the course of the Raman measurements. New Raman features are attributed to TO and LO vibrations of ZnSe nanocrystallites formed in the film under laser illumination. Depending on the laser wavelength and power density, the ZnSe nanocrystallites can experience tensile strain in the film due to a non-thermal photoplastic effect in the As2Se3 film resulting in a partial removal of the material from the laser spot. The tensile strain value, estimated from the TO and LO phonon frequency shift, is shown to reach up to 2.9 GPa.

In-doped As2Se3 thin films studied by Raman and X-ray photoelectron spectroscopies

Amorphous In-doped As2Se3 films with nominal indium contents x up to 7 at.% were prepared by thermal evaporation. Atomic force microscopy studies confirm the uniform film structure with a surface roughness near 5 nm, noticeably higher than for similarly prepared undoped As2Se3 film. X-ray photoelectron spectroscopy (XPS) studies enabled the chemical composition of the films to be examined. As follows from the XPS data, the In content in the film strongly decreases with the film depth. For films with x ≥ 2 at.%, Raman features attributed to transverse and longitudinal optical phonons of InAs are revealed in the Raman spectra as an evidence for the formation of InAs nanocrystallites in the As2Se3:In film under laser illumination.

Characteristics of Amorphous As2S3 Semiconductor Films Obtained via Spin Coating

Centrifugation is used in fabricating, e.g., films with large areas and/or thicknesses of several micrometers. However, it has yet to be widely employed for chalcogenide compounds, due to their relatively weak solubility in most solvents. Determining the optimum conditions for preparing solutions of chalcogenide compounds and obtaining films via centrifugation is therefore of great interest. Specific features of amorphous arsenic sulfide (As2S3) films prepared via the centrifugation of solutions in n-butylamine have been studied. These films were characterized by means of X-ray diffraction analysis, IR spectroscopy, atomic-force microscopy and Raman spectroscopy. It was shown that amorphous As2S3 films have a greater elasticity modulus than those of analogous composition produced via thermal evaporation in vacuum, or As2S3 glass. A structural model based on arsenic sulfide clusters whose surfaces are bound by negatively and positively charged ions is used to explain the experimental results obtained in this work. DC measurements show that the amorphous films exhibit semiconductor-type conductivity. Their room temperature conductivity is ~10−15 S/cm, which indicates good dielectric properties. The films are optically transparent starting from the yellow spectral range, making them promising functional materials for engineering applications in optics and photonics.

Raman evidence for surface oxidation of amorphous As2S3 thin films under ultraviolet irradiation

Amorphous As2S3 films with surface roughness near 0.5 nm were prepared by thermal evaporation. Raman measurements performed under ultraviolet (UV) laser excitation (325 nm) revealed a series of sharp intense peaks appearing at laser power density Pexc above 150 kW/cm2. No such effects were observed at Raman measurements under visible (514.7 or 632.8 nm) light excitation, even for much higher Pexc values. The new Raman peaks are identified as arsenolite (As2O3) features. UV light-assisted oxidation of the As2S3 surface is discussed.

Optical hysteresis in SPR structures with amorphous As2S3 film under low-power laser irradiation

Optical hysteresis is a fundamental phenomenon that can lead to optical bistability and high-speed signal processing. Here, we present a theoretical and experimental study of the optical hysteresis phenomenon in amorphous As2S3 chalcogenide based waveguide structures under surface plasmon resonance (SPR) conditions. The SPR structure is irradiated with low power CW Ar laser radiation at 514 nm wavelength, with photon energy near the optical band-gap of As2S3, in a Kretschmann–Raether configuration. First, we determined the incidence angle on the SPR structure for resonant coupling of the laser radiation within the waveguide structure. Subsequently, by setting the near resonance incidence angle, we analyzed the variation of the laser power reflected on the SPR structure with incident power. We demonstrated that, by setting the incidence angle at a value slightly smaller than the resonance angle, the increase followed by the decrease of the incident power lead to a wide (up to 60%) hysteresis loop of the reflected power. This behavior is related to the slow and persistent photo-induced modification of the complex refractive index of As2S3 under 514 nm laser irradiation. The experimental and theoretical results are in good agreement, demonstrating the validity of the theoretical model presented here.

Особенности характеристик аморфных полупроводниковых пленок As2S3, полученных методом центрифугирования раствора

Особенности характеристик аморфных полупроводниковых пленок As2S3, полученных методом центрифугирования раствора

Preparation of Pure Amorphous As2S3 Films of a Stoichiometric Composition

The results of studying the composition of arsenic trisulphide (As2S3) films obtained by adding finely dispersed copper or silver powders to the starting materials for sputtering or by using triple compositions As–S–As and As–S–Cu are presented. The issues of preserving the composition of the films obtained and the degree of their purity are discussed.

Formation of CdSe nanocrystals in Cd-doped thin arsenic selenide films under laser irradiation

Amorphous Cd-doped As2Se3 films with nominal Cd contents up to 12at.% were prepared by thermal evaporation. Atomic force microscopy studies confirm the uniform film structure with surface roughnesses below 1nm, independent of the Cd content. As shown by energy-dispersive X-ray spectroscopy, the Cd content in the film reveals a strong gradient and decreases with the film depth. For heavily Cd-doped (above 7at.%) As2Se3 films, Raman features attributed to CdSe longitudinal optical (LO) phonon and its overtone (2LO) are revealed in the Raman spectra as an evidence for the formation of CdSe nanocrystallites in the As2Se3:Cd film under above-bandgap or below-bandgap laser illumination. The CdSe nanocrystallites undergo tensile strain due to a photoplastic effect in the As2Se3 film, i. e. partial removal of the material from the laser spot. The tensile strain value, estimated from the LO phonon frequency shift, is shown to reach nearly 2GPa.

Processes of Nucleation of Amorphous As-S Films at Condensation on Carbon Substrates

Processes of Nucleation of Amorphous As-S Films at Condensation on Carbon Substrates

Photoexpansion in amorphous As2S3: A new explanation

Thin amorphous As2S3 films show a giant photoexpansion of ~5% upon femtosecond laser illumination and this expansion remains after switching off the laser beam. To understand the structural modifications which occur during the photoexpansion process we assumed a molecular cluster structure of the amorphous As2S3. The focused femtosecond laser beam induces electrical charge redistribution on the sulfur atoms of each cluster, which increases the electrical repulsion between sulfur atoms, and thus induces an expansion of the clusters, by network reconfiguration, without breaking the bonds. An increase of the van der Waals distance between molecular clusters also takes place.

Surface relief grating formation in amorphous As40S15Se45 and As2S3 films under 0.532 μm wavelength illumination

In this research we have studied the influence of λ = 0.532 μm laser light illumination on the formation and properties of surface relief gratings in amorphous As2S3 and As40Se15Se45 films, as well as a bulk As2S3 sample. The surface relief grating formation was studied for a wide range of grating periods (∼1 – ∼80 μm) for the variable thicknesses of the samples. The examination of the relief depth, Δh, and its dependence on the grating period at constant exposures shows that the impact of sample thickness could manifest itself as a shift in the optimal grating period at holographic surface relief formation (As2S3) and affect the process itself.

Binary Superimposed Gratings Formed by <I>e</I>-Beam Recording in Amorphous AsS Films

Binary Superimposed Gratings Formed by <I>e</I>-Beam Recording in Amorphous AsS Films

Photo-induced formation of surface relief in amorphous As2S3 films

In this report we study the formation of surface relief in arsenic trisulfide films under laser light radiation with modulated polarization direction. The formation of surface relief is obtained with method what is different from holographic recording – only one laser beam with modulated polarization direction was used. Samples with different thickness were made using vacuum evaporation. The photo-induced changes on the surface were initiated by DPSS laser light (λ = 532nm). Profiles of surface reliefs were observed and relief depth dependence on film thickness and exposure was studied.

Possible mechanism of Ag photodiffusion in a‐As2S3 thin films

Abstractmagnified imageMonitoring the silver photodiffusion in thin amorphous As2S3 film is addressed with a new experimental setup. A possible photo‐diffusion mechanism of silver into the a‐As2S3 thin film under green laser diode light (λ = 532 nm) irradiation is proposed. The proposed mechanism is based on a gradual filling of the structural voids existing in the network of the thin chalcogenide layer. This mechanism is supported by XRD measurements, optical absorption, and modeling data.

On the ultraviolet light induced oxidation of amorphous As2S3 film

Illumination of amorphous As2S3 film by ultraviolet light with an overall light intensity on the sample surface of around 10Wcm−2 leads to extensive film oxidation. After 2min of illumination most of As2S3 film of an original thickness at around 0.425μm was converted into a cubic form of As2O3-arsenolite. A considerable amount of arsenolite microcrystals were found at a height of around 2μm and more which indicated a growth of As2O3 microcrystalline particles from the vapor phase.

Photoinduced Volume Changes of Obliquely and Flatly Deposited Amorphous AsSe Films Universal Description of the Kinetics

Recently, we have constructed structural models for flatly deposited amorphous Se (a-Se) and using these configurations we have developed atomic scale model of photoinduced volume changes in this type of films. In this paper the same work on obliquely deposited thin film is presented. Universal description for the kinetics of photoinduced volume change in chalcogenide glasses is proposed based on our results. Our model containing reversible (transient) and irreversible (metastable) parts for kinetics fits well the experimental results of both obliquely and flatly deposited a-AsSe thin films. Finally, we make a brief comment on stretched exponential function which could also provide a quite good fit to experimental data.

Photoinduced Volume Changes of Obliquely and Flatly Deposited Amorphous AsSe Films Universal Description of the Kinetics

Photoinduced Volume Changes of Obliquely and Flatly Deposited Amorphous AsSe Films Universal Description of the Kinetics