S. E. Nikitin

Photoelectric phenomena in ZnO:Al-p-Si heterostructures

Al-doped zinc-oxide (ZnO:Al) films are obtained by magnetron sputtering. Based on an investigation of electrical properties of the films, it is shown that the electron density in these films is as high as 5×1020 cm−3 and is practically constant in the temperature range 77–300 K, which indicates high efficiency of doping ZnO with an Al impurity. It is found that the deposition of thin films (d≈1 µm) on the p-Si(111) surface leads to the formation of heterostructures with the highest photosensitivity of ∼400 V/W at T=300 K, which oscillates in the spectral range 1.3–3.5 eV. With the oblique incidence of linearly polarized radiation, induced pleochroism emerges in such heterostructures. The magnitude of pleochroism oscillates in the range 5–40% (θ≈75°), which is associated with the interference phenomena in the ZnO films. The prospects of using the heterostructures obtained as highly selective photosensors of natural and linearly polarized radiation are considered.

Oscillations of Induced Photopleochroism in ZnO/GaAs Heterojunctions

Anisotype and isotype ZnO/GaAs heterojunctions were formed by magnetron sputtering of thin n-ZnO:Al films on epitaxial layers of n-and p-GaAs. It is shown that the heterostructures obtained have a high photosensitivity (∼5×103 V/W at 300 K) in a wide spectral range (1.5–3.2 eV), which oscillates due to the radiation interference in thin ZnO films. Under oblique incidence of linearly polarized radiation on a ZnO film, photopleochroism is induced in a heterojunction, whose value oscillates within ∼1–55% at θ=85°. The photopleochroism oscillations are also due to the radiation interference in the ZnO film. It is concluded that the heterojunctions obtained are promising candidates for selective photodetectors of linearly polarized radiation.

Photosensitive structures based on single-crystal silicon and phthalocyanine CuPc: Fabrication and properties

Vacuum thermal deposition of phthalocyanine CuPc onto the surface of crystalline silicon and subsequent magnetron sputtering of ZnO:Al are used to form n-ZnO:Al-p-CuPc-n-Si photosensitive structures for the first time. The highest photosensitivity of these structures SUm≈20 V/W is attained if the ZnO side of the structure is illuminated and is observed in the photon-energy range 1–3.2 eV at T=300 K. An induced photopleochroism is observed if the linearly polarized light is incident obliquely on the ZnO side; the magnitude of the photopleochroism oscillates as a result of the interference of linearly polarized light in the ZnO film. It is concluded that the suggested structures have prospects for use in broadband photoconverters of natural light and in rapidly tunable photoanalyzers of linearly polarized light.

Photoelectric Properties of ZnO/CuPc/Si Structures

Abstractn-ZnO:Al/CuPc/n(p)-Si structures were formed using vacuum-evaporation deposition of copper phthalocyanine (CuPc) layers on the surface of n-and p-Si wafers with subsequent magnetron-sputtering deposition of ZnO:Al layers on the CuPc surface. It is shown that the structures obtained exhibit a high photosensitivity (∼80 V/W at T=300 K) in the spectral range 1.65–3.3 eV. The rectification factor and photovoltaic effect in these structures are discussed in relation to the properties of silicon substrates. It is concluded that the contact of phthalocyanine with diamond-like semiconductors (e.g., silicon) are promising for application in wide-band high-efficiency photovoltaic converters.

Lithium incorporation into thin films of vanadium oxides

Thin-film electrodes based on vanadium oxides have been obtained using the thermal oxidation of vanadium films deposited in vacuum. It is established that these electrodes admit the reversible incorporation of lithium from aprotic electrolytes and possess an initial capacity exceeding 250 mA h/g. The electrodes have good prospects for use in thin-film lithium ion batteries.

Fabrication and Photoelectric Properties of n-ZnO:Al/PdPc/p-Si Structures

Photosensitive n-ZnO:Al/PdPc/p-Si structures were fabricated by vacuum sublimation of palladium phthalocyanine with subsequent magnetron sputtering of ZnO:Al films on p-Si substrates. The current transport mechanisms and the photosensitivity of the structures obtained were investigated. It is shown that structures based on PdPc films are promising for photosensitive devices based on contacts between organic and inorganic semiconductors.

Photovoltaic poperties of n-ZnO:Al/PbPc/p-Si structures

Abstractn-ZnO:Al/PbPc/p-Si photosensitive structures are fabricated for the first time. The steady-state current-voltage characteristics and spectral dependences of the relative quantum efficiency of the photoconversion of these structures are studied, and the mechanisms of charge transport and the photosensitivity processes are discussed. It is concluded that they are promising for application as multiband photoconverters of natural light.

Synthesis and characterization of n-ZnO:Al/CoPc/p-Si structures

Photosensitive structures of the n-ZnO:Al/CoPc/p-Si type were synthesized for the first time using vacuum sublimation of cobalt phthalocyanine (CoPc) and magnetron sputtering of a ZnO:Al target. The maximum photoresponse is observed when the structure is illuminated from the side of the ZnO layer and amounts to ≅400 V/W at T = 300 K. Mechanisms of current transfer and peculiarities of the photosensitivity spectrum are considered. It is suggested that the new photosensitive structures can be used in multiband photoconverters of natural radiation with a broad working spectral range.

Fabrication and photosensitivity of heterojunctions based on CuIn3Se5 crystals

Heterojunctions based on p-CuIn3Se5 crystals are fabricated by magnetron sputtering of an n-ZnO:Al target and by putting naturally cleaved n-GaSe thin wafers onto polished surfaces of p-CuIn3Se5 wafers. The current-voltage characteristics and mechanisms of current flow in the diodes under study are analyzed. The photovoltaic effect revealed in the fabricated structures is discussed. It is shown that the fabricated photosensitive heterojunctions are promising for the development of selective analyzers of linearly polarized radiation.

Thin-film photosensitive structures based on a homoconjugated organosilicon polymer-copper phthalocyanine heterojunction

Rectifying photosensitive structures of the ITO/P(Si)/CuPc type have been synthesized based on a heterojunction between a homoconjugated organosilicon polymer P(Si) and copper phthalocyanine CuPc. The maximum voltage responsivity of the samples (∼1 V/W at T = 300 K) was observed when the structure was illuminated from the P(Si) side. In this illumination mode, thin-film photovoltaic converters based on the proposed heterojunction exhibit a fine structure in the photosensitivity spectrum. It is suggested that the new structures can be used as selective photosensors.