Electrical breakdown in amorphous As2S3 films

We investigated the electrical breakdown under d.c. electric fields of amorphous As₂S₃ films about 100–1000 Å thick sandwiched between two aluminium electrodes. It was found that the breakdown field decreased with increases in either the temperature or the thickness of the sample. Attempts were made to fit the observed electrical breakdown voltages with several previously proposed theories of thermal and electrical breakdown. It was found that a satisfactory fit could only be obtained by a modification of Klein's theory provided that the current was observed to depend on the voltage in an exponential manner in accordance with the Poole mechanism in which the carriers are released from high density localized states within the forbidden energy region. According to this modification, the breakdown field should depend inversely on the temperature and this agrees well with the experiment. The formation of localized conducting channels within the sample because of breakdown was verified by taking a scanning electron micrograph of the junction area of the broken film.     

Pulsed light effects in amorphous As2S3: review

Journal of Materials Science: Materials in Electronics - It is known that amorphous chalcogenide materials exhibit unique optical phenomena, including high nonlinearity, photodarkening, and phase...     

Effect of Ag addition on crystallization in As2Se3 glasses

Differential scanning calorimetry (DSC) behaviours of glassy As₂Se₃ containing Ag up to 5 at % were measured at various heating rates. The effect of addition of Ag on crystallization of glassy As₂Se₃ was investigated. The glass transition temperature decreased with increasing Ag content. Crystallization kinetics were analysed on the basis of the two-step process model, where crystal growth takes place after nucleation. For non-doped As₂Se₃ two-dimensional growth of crystal was predominant, while for Ag-doped ones three-dimensional growth was very likely. It was supposed for all glassy Ag-doped samples that crystal nuclei exist, though micro-crystallites were not observed on X-ray diffraction traces. The activation energy for crystallization and the glass-forming tendency decreased by the addition of Ag.     

Effect of SO2 impurity on the optical transmission of As2S3 glass

To assess the effect of sulfur dioxide impurity on the optical properties and absorption spectrum of glassy arsenic sulfide, we have prepared As₂S₃ glass samples containing 0.01 to 0.12 wt % SO₂ and have measured their transmission spectra in the range 500–5000 cm^?1. The extinction coefficient of sulfur dioxide in glassy arsenic sulfide, evaluated from the intensity of the 1158-cm^?1 absorption band, is 10.0 ± 0.7 cm^?1/wt%.     

Ellipsometry and optical measurements on amorphous thin films of As2Se3

Thin films of amorphous AsSe_3/2 have been prepared by thermal evaporation of the material under a vacuum of 1.33×10^?3 Pa. Reflectivity, transmission and ellipsometric measurements of the films have been carried out. The optical energy gap and the absorption coefficient as a function of wavelength were obtained. Two absorption bands were observed and interpreted in terms of defects in the AsSe_3/2 system (homopolar bonds). Analysis of reflection and transmission spectra shows that the electron density at band tails of both conduction and valency bands follows N(E)?E^1/2 (Taue plots). No considerable variations were observed on changing the film thickness.     

Effect of preparation conditions on the low frequency Raman spectrum of glassy As2S3

Low frequency Raman scattering was measured for glassy As2S3 samples, prepared by different quenched conditions. It was found that the boson peak position shifts to lower energy with increase of the initial temperature of the melt and with increase of quenching rate. The effect is interpreted in terms of the dissociation reaction of As2S3 at high temperature. This leads to softening of the elastic modules and a decrease in the sound velocity.     

Ag掺杂对新型SnO2压敏材料的电学性质的影响

烧渗银电极对压敏电阻的性能是有很大影响的.为了弄清Ag对(Co、Nb)掺杂的新型SnO2压敏材料电学性质的影响,做了组分为SnO2+1.50%CoCl2*6H2O+0.10%Nb2O5+x%Ag2O(x=0.00、0.02、0.50和1.00)的系统实验.当AgO的含量从0.00增加到1mol%时,(Co, Nb)掺杂SnO2压敏电阻的击穿电压从349V/mm增大到429V/mm,1kHz时的相对介电常数从2240减小到1560.晶界势垒高度测量揭示,SnO2的晶粒尺寸的迅速减小是击穿电压急剧增高和介电常数迅速减小的主要原因.对Ag掺杂量增加引起SnO2晶粒减小的根源进行了解释.     

Investigation of surface activity and photoinduced diffusion of metals in solution deposited amorphous films of As2S3

Surface activity of solution deposited (SD) amorphous films of As₂S₃ has been investigated. Silver and copper are readily deposited on such films from appropriate aqueous ionic solutions. The metals diffuse into the films upon irradiation with energetic photons. Structure and properties of SD films have been investigated using electron microscopy, optical spectroscopy and differential scanning calorimetry. The amorphous films tend to crystallize upon metal diffusion. The stability of amorphous films, the deposition of metals on their active surfaces and the photo-induced diffusion may all be attributed to the presence or production of charged defects in amorphous chalcogenide films.     

Optical properties and electrical transport in intercalated amorphous carbon

Iodine and sulfur incorporated amorphous carbon (a-C) films are prepared by vapor phase pyrolysis of carbon rich organic precursor, maleic anhydride. Transmission electron microscopy (TEM) analysis depicts the intercalation induced local structural ordering and evolution of nano-graphitic phases in the sample. An X-ray photoelectron spectroscopy (XPS) study on these samples confirms the presence of intercalates. The study of optical properties of the samples by UV–vis absorption spectrometry accounts for a decrease in optical bandgap and Urbach energy with impurity incorporation and increase in pyrolysis temperature. This refers to induced structural ordering, decrease in disorder and increase in sp² or π-sites in the sample. Electrical conductivity measurement on a-C samples reveals increase in conductivity with pyrolysis temperature induced by iodine and sulfur incorporation.     

AsK-edge EXAFS study of the ternary system Sb2S3–As2S3–Tl2S

The local environment of arsenic atoms in vitreous samples of the system Sb₂S₃–As₂S₃–Tl₂S has been studied by EXAFS at the AsK-edge. The crystalline compound Tl_5.6As₁₅S_25.3 situated within the zone of glass formation of the Sb₂S₃–As₂S_3–Tl₂S phase diagram was used as reference compound in order to derive appropriate phase and amplitude functions. The structure parameters determined were the number of first neighbours N _As–S, the arsenic-sulphur distance, R _As–S, and the Debye-Waller factor, σ_As–S. The influence of the glass-forming antimony sulphide Sb₂S₃ and the glass-modifying thallium sulphide Tl₂S on the As₂S₃ host matrix has been shown. This revised version was published online in November 2006 with corrections to the Cover Date.     

Specific features of the photodielectric effect in amorphous As2Se3 layers

The photodielectric effect (PDE) in amorphous arsenic triselenide (As₂Se₃) layers has been studied in a weakly varying electric field. As the field frequency decreases in the infra-low-frequency range, the experimentally measured function of relative conductivity coincides with the theoretically predicted behavior. It is established that the frequency dependence of the recombination coefficient exhibits a minimum.     

Binary phase spatial modulation using photoinduced anisotropy in amorphous As(2)S(3) thin film

We present a method for binary phase spatial modulation that uses photoinduced anisotropy in a chalcogenide amorphous As(2)S(3) thin film and its application to binary phase-only filters in a VanderLugt optical correlator. The time-dependent light-transmission properties of the photoilluminated As(2)S(3) thin film are analytically examined by use of third-order nonlinear polarization theory. Experimental results on optical correlation are discussed.     

Optical properties and photoinduced changes in amorphous AsS films

The dependence on composition of optical properties and photoinduced changes in thin films of As_xS_100?x with x between 15 and 45 were investigated. The optical band gap and the single oscillator fitting constants show extreme at the stoichiometric composition x = 40 and they vary almost linearly with sulphur content in specimens containing an excess of chalcogen. In contrast, irreversible and reversible photoinduced changes of the optical properties accompany a characteristic transition at x ≈ 30. This suggests that the origin of these effects is attributable to transformations of AsS and SS bonds in films containing an excess of chalcogen. This speculation is supported by thermal analyses.     

The growth and electrical properties of single crystal Cd3As2 platelets

Single crystal platelets of Cd₃As₂ having carrier concentrations less than 10²⁴ m⁻³ have been grown from the vapour in the presence of argon gas and excess cadmium vapour. It is shown that the resistivity and Hall data is consistent with a band model in which there is a direct band-gap atk=0 of approximately 0.38 eV and an indirect zero band-gap. It is suggested that the large electron carrier concentrations usually present in Cd₃As₂ result from anti-structure disorder.     

Photo-induced changes in optical properties of As2S3 and As2Se3 films deposited at normal and oblique incidence

Photostructural transformations in amorphous chalcogenide films have been a subject of intensive research so far. In this paper we discuss the changes in the optical properties of typical As-based chalcogenide glasses (As₂S₃ and As₂Se₃) on exposure to ultraviolet (UV) light. An attempt has been made to systematically investigate the optical parameters like extinction coefficient, refractive index and optical bandgap of the films by measuring the same for as-grown and UV-exposed amorphous films of As₂S₃ and As₂Se₃ prepared by vacuum evaporation technique.