Electrical and photoelectric properties of heterostructures NiO/p-CdTe and NiO/n-CdTe

In this study, we investigate the electrical and photoelectric properties of heterostructures formed by the reactive magnetron sputtering of thin film NiO onto p-CdTe and n-CdTe substrates. The current-voltage characteristics of the heterojunctions were measured at room temperature. The dominating current transport mechanisms through the NiO/n-CdTe and NiO/p-CdTe heterojunctions at the forward biases are generation-recombination and tunnel, at the reverse biases is tunnel current transport mechanisms. The heterojunctions under investigation generate open-circuit voltage Uoc = 0.26 V and short-circuit current Isc = 58.7 μA/cm2 under illumination 80 mW/cm-2. The research results can be used for better understanding of the processes occurring in heterojunctions NiO/ n-CdTe and NiO/p-CdTe, to further improve their properties and parameters

Electrical properties anisotype heterojunctions n-TiO2:Mn/p-CdTe

The authors have investigated electronic properties of n-TiO2:Mn/p-CdTe anisotype heterojunctions, produced by the method of electron-beam evaporation of TiO2:Mn film on single-crystal CdTe substrates in vacuum. The dominant mechanism of charge transport in the forward and reverse bias has been established

Study on Cu2ZnSnSe4 crystals and heterojunctions on their basis

The most promising materials for the solar radiation converters are such compounds as CdTe and Cu(In, Ga)Se2, CuIn(S, Se)2, CuGa(S, Se)2 solid solutions. However, the uneconomic nature of Cd, Te and the limited supply of In and Ga, as well as their high cost, force researchers to replace In and Ga with the more common elements of II and IV groups, namely Zn and Sn. Apart from that, researchers are now testing such new semiconductor compounds as ZnSnS4, Cu2ZnSnSe4, and solid solutions on their basis. These compounds have a band gap width (Eg ≈ 1.5 eV) close to optimal for the conversion of solar energy, a high light absorption coefficient (≈ 105cm-1), a long lifetime and a high mobility of charge carriers. Moreover, the interest in such semiconductor heterojunctions as TiO2/ZnSnS4, which have several advantages over homo-transitions, is steadily growing at present. The paper presents results studies of kinetic properties of Cu2ZnSnSe4 crystals. We fabricated n-TiO2/p-Cu2ZnSnSe4 anisotype heterojunctions, determined their main electrical parameters and built their energy diagram. The Cu2ZnSnSe4 crystals have p-type conductivity and the Hall coefficient practically independent of temperature. The temperature dependence of the electrical conductivity σ for Cu2ZnSnSe4 crystalsis metallic in character, i. e. σ decreases with increasing temperature, which is caused by a decrease in the mobility of the charge carriers with the growth of T. Thermoelectric power for the samples is positive, which also indicates the prevalence of p-type conductivity. In this study, the n-TiO2/p-Cu2ZnSnSe4 heterojunctions were produced by reactive magnetron sputtering of a thin TiO2 film on the Cu2ZnSnSe4 substrate. The energy diagram of the investigated n-TiO2/p-Cu2ZnSnSe4 anisotype heterojunctions was constructed in accordance with the Anderson model, without taking into account the surface electrical states and the dielectric layer, based on the values of the energy parameters of semiconductors determined experimentally and taken from literary sources. The authors have also investigated electrical properties of the heterojunctions: the value of the potential barrier was determined, the value of the series resistance and shunt resistance (respectively, Rs = 8 W and Rsh = 5.8 kW) at room temperature. The dominant mechanisms of current transfer were established: tunneling-recombination mechanism in the voltage range from 0 to 0.3 V, and over-barrier emission and tunneling with inverse displacement in the voltage range from 0.3 to 0.45 V

ELECTRICAL AND PHOTOELECTRIC PROPERTIES OF HETEROJUNCTIONS MOOX/N-CD1-XZNXTE

The paper presents the results of studies of the optical and electrical properties of МоOx/n-Cd1-хZnхTe semiconductor heterojunctions made by depositing MoOx films on a pre-polished surface of n-Cd1-хZnхTe plates (5 × 5 × 0.7 mm3) in a universal vacuum installation Leybold - Heraeus L560 using reactive magnetron sputtering of a pure Mo target. Such studies are of great importance for the further development of highly efficient devices based on heterojunctions for electronics and optoelectronics. The fabricated МоOx/n‑Cd1‑хZnхTe heterojunctions have a large potential barrier height at room temperature (φ0 = 1.15 eV), which significantly exceeds the analogous parameter for the МоOx/n-CdTe heterojunction (φ0 = 0.85 eV). The temperature coefficient of the change in the height of the potential barrier was experimentally determined to be d(φ0)/dT = -8.7·10-3 eV K, this parameter is four times greater than the temperature coefficient of change in the height of the potential barrier for MoOx/n-CdTe heterostructures. The greater value of the potential barrier height of the МоOx/n-Cd1-хZnхTe heterojunction is due to the formation of an electric dipole at the heterointerface due to an increase in the concentration of surface states in comparison with MoOx/n-CdTe heterostructures, and this is obviously associated with the presence of zinc atoms in the space charge region and at the metallurgical boundary section of the heteroboundary. In МоOx/n‑Cd1-хZnхTe heterojunctions, the dominant mechanisms of current transfer are generation-recombination and tunneling-recombination with the participation of surface states, tunneling with forward bias, and tunneling with reverse bias. It was found that МоOx/n-Cd1-хZnхTe heterojunctions, which have the following photoelectric parameters: open circuit voltage Voc = 0.3 V, short circuit current Isc = 1.2 mA/cm2, and fill factor FF = 0.33 at an illumination intensity of 80 mW/cm2 are promising for the manufacture of detectors of various types of radiation. The measured and investigated impedance of the МоOx/n-Cd1-хZnхTe heterojunction at various reverse biases, which made it possible to determine the distribution of the density of surface states and the characteristic time of their charge-exchange, which decrease with increasing reverse bias

Fine Art of Thermoelectricity

A detailed study of hitherto unknown electrical and thermoelectric properties of graphite pencil traces on paper was carried out by measuring the Hall and Seebeck effects. We show that the combination of pencil-drawn graphite and brush-painted poly­(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) films on regular office paper results in extremely simple, low-cost, and environmentally friendly thermoelectric power generators with promising output characteristics at low-temperature gradients. The working characteristics can be improved even further by incorporating n-type InSe flakes. The combination of pencil-drawn n-InSe:graphite nanocomposites and brush-painted PEDOT:PSS increases the power output by 1 order of magnitude

The properties of metal contacts on TiO2 thin films produced by reactive magnetron sputtering

The article deals with research on volt-ampere characteristics of metal contacts (Al, Cr, In, Mo, Ti) on titanium dioxide thin films and influence of annealing in vacuum on their electric properties. Volt-ampere characteristics measurements were taken by three-probe method. There was established that indium contact on TiO2 thin films possessed sharply defined ohmic properties