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In this research, we examined metallic back contacts effects on the electrical characteristics of heterojunctions in the context of solar cells. Gold, silver, aluminum and copper were selected as substitutes for the conventional molybdenum. Heterojunctions with SnS and ZnS as an absorber and buffer layers, respectively, were fabricated using spray pyrolysis. The characterization revealed the formation of SnS in an orthorhombic structure and ZnS in a cubic structure, displaying preferential orientations along (120) and (222) planes, respectively. These structures exhibited excellent crystallinity, evidenced by large crystallite sizes and phase purity, as confirmed by morphological study. Optical measurements indicated the band gap for SnS and ZnS as 1.5 and 3.1eV, respectively. Additionally, through Hall Effect and Mott–Schottky analysis, it was observed that the SnS and ZnS films displayed p-type and n-type conductivity, with corresponding carrier concentrations of $1.87\times 10^{18}$ and $1.41\times 10^{19}$cm${}^{-3}$, respectively. The electrical characteristics of the n-ZnS/p-SnS heterojunction were explored through forward I–V analysis. Photocurrent measurements revealed that the constructed structures demonstrated rectifying behavior. The resistance series and ideality factor values obtained were observed to be relatively high. The unusual ideality factor can be attributed to the formation of Schottky contact between contacts (Ag, Al, Cu) and SnS film, possibly due to defects at the interface state of ZnS/SnS. This study’s findings indicate that, among the tested FTO/ZnS/SnS heterojunction structures, with Au metal contact exhibited superior performance. It suggests that Au could serve as a viable alternative to Mo as the back metal contact for SnS-based solar cells.

Based on density functional theory, we have calculated and analyzed the electrical characteristics of silicon (100) - 2×1 surfaces. The calculation results show that the sulfur atom establishes a Schottky-like contact when it is used to tethering the surface and the molecule. In contrast to the Si – S linkage, a direct Si – C linkage does not build up a barrier between the molecule and the surface of silicon. This type of contact is a Ohmic-like contact. The origin of the characteristics of the contacts is analyzed. A basic rule for designing the electrical characteristics of the molecule - surface of silicon is presented.

There is considerable interest in electrical sensing of biomolecular binding since it has the potential to be label free, to work easily in aqueous environments native to the biomolecules, and to be integrated with small, fast, and inexpensive microelectronoics as detection instrumentation. Although electrochemical methods have been used successfully in detections of DNA molecules with Ag labels at very high sensitivity (~ p ml), detection of DNA molecules in terms of label free techniques has a lower sensitivity (~ μ ml). Here, the surface attachment chemistry is critical towards the detection of ultra-low concentration of biomolecules. In this article, based on density functional theory, we have calculated and analyzed the electrical characteristics of the contact between aromatic molecules and silicon (100) − 2×1 surfaces. Design principles for silicon based electrodes of electrochemically biomolecular sensing instruments for label-free sensing of single or a few biomolecular molecules have also been discussed.

We have found that Scandium metal is near ohmic as deposited on GaN, but when it is annealed at high temperatures a large barrier height Schottky forms. In this study we used Sc-Au contacts to form Schottky barrier diodes on AlGaN/GaN HEMT material. We have found that the morphology remains unchanged even after an 800 degrees centigrade anneal. This investigation has revealed that the reverse leakage current of this metal system is an order of magnitude lower than a conventional Ni-Au contact and supports a reverse breakdown that is 1/3rd larger. The similarity of the anneal temperatures to ohmic contacts enable gates and contacts to be annealed at the same time thus simplifying processing. The lack of morphology change supports the use of Sc-Au for E-beam alignment marks as well. Diode contacts on AlGaN/GaN with Schottky-ohmic separation of 10 microns demonstrated reverse breakdown in excess of 100V when the contacts were annealed at 800C. These results suggest this metallization may have applications as a new HEMT gate metal, and Schottky diodes.

Bulk ZnO has traditionally been regarded as multifunctional materials for energy and optoelectronics applications. Recently, exploring this material at the nanoscale has been reported and seeking a proper substrate is highly desired. In this work, the structural and electronic properties of graphene like ZnO two-dimensional (2D) monolayer are investigated by first principles calculation based on density functional theory. The alignment of the valence and conduction bands of ZnO with the state of Cu substrate is analyzed. Particularly the attention has been focused on the establishment of a Schottky contact and interfacial charge transfer between the 2D ZnO monolayer and Cu substrate. It is predicted that the electronic charges are accumulated on the Zn and O atoms due to d–d hybridization between Cu and Zn. Our study reveals that the significant interaction between the ZnO and Cu can greatly modify the electronic properties of the ZnO and suggests potential applications in nanoelectronic devices.

We have investigated the heterointerface properties of recently developed hybrid solar cells comprising a Schottky contact made of transparent conductive polymer (TCP) and an underlying GaN semiconductor layer. The heterointerface capacitance induced by the depletion layer under the TCP Schottky contact showed a rapid drop at a specific frequency. An intrinsic capacitance component that was derived from the capacitance–frequency (C–f) characteristics of the heterointerface showed clear correlation with the open circuit voltage. Hence, the C–f characterization using TCP Schottky contacts is indicative of the quality of the heterointerface.

Ultraviolet (UV) detection characteristics of Ag Schottky contacts with ZnO nanorods (ZnO-NRs) grown on Indium Tin Oxide (ITO)-coated glass substrates have been investigated. A low-temperature hydrothermal method was used for growing ZnO-NRs. Circular contacts of Ag were deposited above the ZnO-NRs/ITO samples using the shadow mask technique. The structural properties of the ZnO-NRs were characterized by using scanning electron microscopy (SEM), atomic force microscope (AFM) and X-ray diffraction (XRD). The results revealed a (0002) crystal orientation and a wurtzite hexagonal structure. The electrical characteristics of the Ag/ZnO-NR Schottky contacts were studied at forward applied bias over the range 0V to 1V, under dark and UV illumination. The dark and photocurrents were $1.29\times 10^{-5}$A and $2.16\times 10^{-5}$A, respectively, and the contrast ratio (ratio of photocurrent to dark current) was 1.67 at $+$1.0V for these devices. The results show that these devices could be useful for cost-effective and low-voltage UV detection applications.

Based on density functional theory, we have calculated and analyzed the electrical characteristics of silicon (100) – 2×1 surfaces. The calculation results show that the sulfur atom establishes a Schottky-like contact when it is used to tethering the surface and the molecule. In contrast to the Si – S linkage, a direct Si – C linkage does not build up a barrier between the molecule and the surface of silicon. This type of contact is a Ohmic-like contact. The origin of the characteristics of the contacts is analyzed. A basic rule for designing the electrical characteristics of the molecule – surface of silicon is presented.

There is considerable interest in electrical sensing of biomolecular binding since it has the potential to be label free, to work easily in aqueous environments native to the biomolecules, and to be integrated with small, fast, and inexpensive microelectronoics as detection instrumentation. Although electrochemical methods have been used successfully in detections of DNA molecules with Ag labels at very high sensitivity (∼ p ml), detection of DNA molecules in terms of label free techniques has a lower sensitivity (∼ µ ml). Here, the surface attachment chemistry is critical towards the detection of ultra-low concentration of biomolecules. In this article, based on density functional theory, we have calculated and analyzed the electrical characteristics of the contact between aromatic molecules and silicon (100) – 2×1 surfaces. Design principles for silicon based electrodes of electrochemically biomolecular sensing instruments for label-free sensing of single or a few biomolecular molecules have also been discussed.