Approximately spherical nanoparticles of the II–VI semiconductor materials Cd1-xZnxS have been produced
successfully by laser ablation of the bulk material in several liquids. The non-stabilized suspensions of particles are
characterized by absorption spectroscopy and transmission electron microscopy (TEM). The procedure is not strongly
size-selective, radii of 7±3 nm were found for Cd1-xZnxS by transmission electron microscopy. Acetonitrile stabilizes
the particles for several days up to weeks. Prolonged irradiation leads effectively to a reduction in particles size, in
which particle agglomeration may play an important role. Ablation in degassed liquids does not have a significant effect
on the absorption of the suspended particles.
In recent years, resumed intensive studies of heterojunctions, in connection with the possibility of using them on the most economical and relatively efficient photodetectors. In this economy is determined by the structure of production technology and the value of the source material. Thus there is a substitution reaction on the surface of the films Cd1-xZnxS formed a second layer of Cu2S, whose thickness is determined by the time of deposition. When light 1,45⋅104 lux photocells studied Cu2S-Cd1-xZnxS and Cu2Se-Cd1-xZnxSe generated voltage 0,5÷0,6V and in 0,45-0,58V, current Jsc 15 ÷ 20 mA/sm2 and 12-15mA/cm2 and efficiency were = 11%. and 8%. respectively. It is established that with increasing content of Zn in the base material-circuit voltage Uos photocell increases and short-circuit current decreases. Using as a base material of solid solutions of Cd1-xZnxS and Cd1-xZnxSe causes an increase in the potential barrier at the contact.
In this work the results on the investigation of the photosensitivity near the IR region of the CdSe1-xTex (O less than or equal to x less than or equal to O.4) films.
with thickness 0.5÷2μm, prepared on glass-ceramic substrates by precipitation from aqueous solution are presented. The
temperature dependence of dark and light conductivity, spectrum of primary and impurity photoconductivity has been
investigated.
In the present work the photochemical reaction in Cd1-xZnxS(Se) films considered depending on technological modes of their deposition and heat treatment (HT). In Cd1-xZnxS(Se) films the formation of Cdi-Cdi, Zni-Zni, VSe-Zni etc. associations provides occurrence of optical active electronic states carried in an interval of energy 0.3-0.6 eV allows using of a Cd1-xZnxS(Se) films for creation on their basis non-cooled photodetectors in the IR-range. At illumination by light of λ=0.95 μm were observed anomalous photoconductivity and photomemory phenomenon connected with existence in them defects with metastable states which concentration can be operated depending on structure deposition and heat treatment (HT) mode and limits by tunnel transitions of no basic located electrons and holes between r- and s-centres. In Cd1-xZnxS(Se) films after HT on air during 10-15 minutes was observed the photochemical reaction with activation energy of 0.17-0.21 eV representing disintegration process of donor-acceptor pairs consisting of the r-centres and the Cdi, Zni donors at illumination with light of λ=1.25 μm and caused by precipitation conditions and HT.
In the present work the features of an impurity and induced impurity photoconductivities in IR region, and also anomalous photoconduction and photochemical reaction in Cd1-xZnxSe films are considered depending on film deposition and heat treatment (HT) modes. The formation of Cdi-Cdi, Zni-Zni, Vse-Zni etc. associations in Cd1-xZnxSe films, providing occurrence of optical active electronic states, carried in an interval of energy 0.3÷0.6 eV, allows to use of these films for creation non-cooled photodetectors of IR-range. At illumination of films by λ=0.95 μm light, the anomalous photoconductivity and photomemory phenomenon were observed, connected with defects of metastable states, which concentration can be controlled by film structure, deposition and HT modes, and limits by tunnel transitions of no basic located electrons and holes between r- and s-centres. The photochemical reaction with activation energy of 0.17÷0.21 eV, was observed at illumination (by λ=1.25 μm light) of Cd0.8Zn0.2Se films heart treated on air during 10÷15 minutes. It represents a disintegration process of donor-acceptor pairs, consisting r-centres and Cdi, Zni donors, and caused by precipitation conditions and HT.
The negative infrared photoconductivity (NPH) has been observed for the first time in CdS1-xSex films, in the wavelength region of 0.700 ÷ 1.23 μm. at values of stimulating light intensity Φ = 100 ÷ 400 Lk. electrical field E = 0.5 ÷ 130 V/cm and temperature T = 265 ÷ 310 Κ. It is established, that basic laws of NPH explains on the basis of two-barrier model and in the considered conditions a charge carriers, overcome a barrier by tunneling. A films of CdS1-xSex can be used in IR engineering and negatronics.
The Cd1-xZnxSe films, deposited from solution, differ by high photosensitivity in visible and near IR region of spectrum. In present paper are called the results of induced impurity photoconductivity (IIP) of Ccd1-xANxSe (0 less than or equal to x less than or equal to 0.5) films in region of 2.5-3.0micrometers . The Cd1-xZnxSe films are obtained on glass-ceramic substrates by chemical deposition from aqueous solution, containing cadmium and zinc salts, and thiourea. The films are subjected to heat-treatment in air at temperatures 400-500 degree(s)C for 0-30 min. A quasi-linear spectrum of IIR adjoins to band according to impurity band from the side of high energy. At the spectrum of IIP have been observed narrow bands, the half-wide is 0.03-0.04 eV. With increasing the levels of primary photoexcitation the deformation of IIP spectrum to region of high energy, which appears in bands spectrum maximum. The value of violet shear is equal to (Delta) E=0.05 eV. The values of these phenomena are determined by nature of multi- levels associate, which are related to the optical activated sticking centers of electrons. At the same time the intensity of wide IIP band (hvo=0.3eV, in a low- temperature region) weak dependancies on temperature, on which testily band-impurity character of ionization of according ionizated donor centers. The isolated donors characterized by level of Ec=0.29-0.32 eV and cross- section of capture (Sn=(2-4)x1017 m2). Their participation in called associated provides appearance of systems of optical active electron states, entered in energy range of 0.3-0.6 eV, having conditioned by high-temperature stable photosensitivity of Cd1-xZnxSe films in IR-region. It is shown that, the studied Cd1-xZnxSe films could be in use as an ordinary and cheap elements of memory of optical records, transformers of visible light to infra-red (IR) radiation.
In this work the results on the investigation of the photosensitivity near the IR region, of CdS1-xSex (0 less than or equal to x less than or equal to 0.4) films 8 divided by 9 micrometers thick prepared on glass-ceramic substrates by precipitation from aqueous solutions are presented. The temperature dependence of dark and light conductivity, spectrum and optical quenching of primary and impurity photoconductivity are investigated. The obtained results show that when controlling ionic composition and heat-treatment (HT) conditions, one can purposely control the properties of CdS1-xSex (0 less than or equal to x less than or equal to 0.4) films, achieve the appropriate degree of compensation of different recombination levels and traps attributed to intrinsic defects or impurities, which result in high level of photoelectrical parameters near the IR region. Just after deposition the photoconductivity spectrum maximum of CdS1-xSex (0 less than or equal to x less than or equal to 0.4) films is observed at (lambda)1=0.495 divided by 0.545 micrometers versus the film composition. Subsequent to HT, the photoconductivity spectrum considerably widens and appears the impurity maximums at (lambda)2=0.58 divided by 0.69 micrometers and (lambda)3=0.95 divided by 1.05 micrometers. At (lambda)=0.88 divided by 1.56 micrometers wavelength region, the primary photocurrent optical quenching (POQ) of the films takes place. The POQ spectrum in photosensitive CdS1-xSex films consists band with the maximum at (lambda)max-1.28 divided by 1.38 micrometers, versus the film composition and HT conditions. At optimum conditions, the degree of quenching attains to 12%. The quenching of the primary photoconductivity by infrared light, leads to the occupation of the r-centers by holes.
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