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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.

By developing photocatalyst systems that enhance the photocatalytic activity for the degradation of antibiotics, our interest currently lies in utilizing visible light to optimize the use of the solar light spectrum. Bismuth-based photocatalysts take advantage of nature’s narrow bandgap and wide range of compounds. In this study, the synthesis of bismuth-based heterojunctions from two visible light response Bi₂O₃ and Bi₂O₂S materials by hydrothermal method is used for the degradation of tetracycline. The highest removal efficiency belongs to the Bi₂O₃/Bi₂O₂S heterojunction hydrothermal in 6 h, which is 51.27%. The combination of Bi₂O₃ and Bi₂O₂S materials creates the heterojunction that enhances the visible light response up to 623 nm, reduces the recombination rate, increases carrier mobility, and tunes the energy level. In addition, the photocatalytic degradation of Bi₂O₃/Bi₂O₂S systems involves e${}^{-}$, h${}^{+}$, $\gamma$OH, and $\gamma$O${}_2^{-}$ in the degradation of tetracycline. The Bi₂O₃/Bi₂O₂S is a promising heterostructured photocatalyst in the removal of tetracycline from wastewater.

FIR photon detector development starting from the extrinsic detectors for LWIR to FIR wavelengths are presented. Several other types of IR detectors, including the cut-off wavelength extension into the FIR range for quantum well infrared photodetectors (QWIPs), are summarized. Efforts in developing p-GaAs homojunction interfacial workfunction internal photoemission (HIWIP) far-infrared detectors and the most reason developments on GaAs/AlGaAs Heterojunction interfacial workfunction internal photoemission (HEIWIP) far-infrared detectors are presented.

Energy efficient hetero-junction tunneling transistors in a simple "cross-point" configuration that utilizes top gates are analyzed for use at extremely scaled sub-10 nm gate-lengths. The active tunneling region comprises of a vertical p++/n+ heterojunction (for example formed at the cross point of p++SiGe/n+Si), where modulation of the energy-bands in the gated n+Si region with a top-gate is used to control the degree of band overlap and tunneling distance and hence current. The sub-threshold swing characteristic of these devices is shown to be potentially highly immune to extreme downscaling to 6 nm gate length allowing for an intact and efficient switching behavior to be retained. The extreme scalability and ultra-low voltage operation could make such cross-point devices useful for alternative applications and architectures that require ultimate energy efficiency.

The binding energy of the ground state of a bound polaron near the interface of a polar-polar semiconductor heterojunction is investigated by using the Lee–Low–Pines intermediate coupling method. The influence of a triangular potential approximation of the interface, the electron-phonon and impurity-phonon interactions as well as the half-space bulk longitudinal and interface-optical phonon modes are all taken into account. We have performed numerical calculations on the GaAs/Al_xGa_1-xAs(0.2 ≤ x ≤ 0.4) heterojunction system and studied the relations between the ground state binding energy of the polaron and the impurity position, electric field strength and electron area density, respectively. It is found that with the increase in the distance between the impurity and the interface, the binding energy and the contribution of phonons reach the maximum. It is also found that the binding energy of the bound polaron increases slowly with the increase in an electric field while the total polaronic correction decreases the binding energy. When the electron area density is increased, the contribution of the interface-optical (IO) modes is greater than that of the bulk longitudinal optical (LO) mode.

The donor/acceptor heterojunction devices having configuration n-PANI/p-PSi were fabricated by in-situ chemical oxidative polymerization method of aniline on p-type porous silicon. The structure of n-PANI/p-PSi junctions was examined by scanning electron microscopy and X-ray diffraction spectroscopy. The dark current-voltage measurements were performed in the temperature range of 303–393 K to determine the electrical transport mechanisms of these devices. Rectifying properties were obtained and capacitance–voltage at 1 MHz behavior indicates an abrupt interface. At low forward bias, the current was found to be limited by thermionic emission of holes from p-PSi over the PANI/PSi barrier in the PANI thin film. For relatively higher voltage, the conduction was dominated by a space charge limited current mechanism, with an exponential distribution of traps. Also, various electrical parameters were determined from the I-V and C-V analysis.

Epitaxial layers of ZnTe have been grown on a (111) oriented CdTe single crystal substrate by thermal evaporation technique at 180°C and a pressure of 10^-6 Torr. X-ray diffraction pattern indicated a highly oriented crystallographic growth of ZnTe (111) layer on CdTe (111) substrate. C–V measurements are carried out at frequencies of 10 kHz and 100 kHz. 1/C² versus the forward bias voltage gave a straight line in the voltage range from 1 to 3 V. Extrapolation of 1/C² → 0 led to an estimated value of the built-in potential of about 0.58 V. The calculated charge carrier concentration in the lightly doped over-grown layer, ZnTe, has been found to be p = 1.7 × 10¹⁶cm^-3. It was found that energy band diagram constructed according to the electron affinity model is not the adequate one to explain the capacitance–voltage behavior. Therefore, one should take into account the effect of interface states on the energy band diagram. The interface states density has been estimated to be ~10¹³cm^-2 for (111) ZnTe/(111)CdTe heterojunction system. The interface states were identified as hole traps for the ZnTe/CdTe heterojunction. Accordingly, a band bending downward both materials, and a depletion zone in both of them are expected.

La${}_{0.9}$Hf${}_{0.1}$MnO₃ films were grown on 0.05 wt.% Nb-doped SrTiO₃ substrates by pulsed laser deposition. X-ray diffraction measurements demonstrated that our samples were of good epitaxy and single-crystal. The temperature-dependent resistance has been investigated. It was observed that the as-grown film of La${}_{0.9}$Hf${}_{0.1}$MnO₃ exhibited a typical paramagnetic-ferromagnetic transition. Heterojunctions of La${}_{0.9}$Hf${}_{0.1}$MnO₃/0.05 wt.% Nb-doped SrTiO₃ exhibited-asymmetric current–voltage characteristics and a remarkable temperature-dependent rectifying behavior in a wide temperature range (from 40 K to 300 K). And the most remarkable observation of this work is the existence of a crossover from positive to negative magnetoresistance in the La${}_{0.9}$Hf${}_{0.1}$MnO₃/0.05 wt.% Nb-doped SrTiO₃ heterojunction as the temperature decreases. A temperature-dependent magnetoresistance was studied as well. The rectifying characteristics and tunable magnetoresistance of these heterojunctions may be attributed to band structure of La${}_{0.9}$Hf${}_{0.1}$MnO₃/0.05 wt.% Nb-doped SrTiO₃ heterojunction.

In this study, indium tin oxide (ITO) was deposited onto sapphire and low resistive p-Si substrates using pulsed laser deposition (PLD) technique. The optical energy gap of ITO deposited on the sapphire substrate was 3.7 eV at room temperature. Photoluminescence (PL) of ITO shows an emission of broad peak at 524 nm. Photovoltaic (PV) characteristics of the n-ITO/p-Si heterojunction are examined and showed conversion efficiency $(\eta )$ of 1.8%. The open circuit voltage $(V_{\mathrm{\text{OC}}})$ for this cell was 0.49 V while the short circuit current density $(J_{\mathrm{\text{SC}}})$ was 17.4 mA/cm². The fill factor of this cell was 22%. The ideality factor of ITO/Si heterojunction is about 3.1. The barrier height ${\mathrm{\Phi }}_B$ of the heterojunction was determined from I–V characteristics and was 0.83 eV. The responsivity of the heterojunction was measured and the maximum value of responsivity was 0.5 A/W without bias voltage. The minority carrier lifetime of the solar was measured using open circuit voltage decay (OCVD) method and found to be 227 $\mu$s.

The photoelectric properties of ZnO-doped WSe₂ thin films created on Si substrates by a thermal evaporation method were investigated. The effects of ZnO on the surface morphology, structure, photoluminescence, light absorption characteristics and electrical properties of WSe₂ thin films were analyzed. It is found that the nucleation density and the crystallinity of the ZnO-doped WSe₂ nanowires are higher than without doping, and the electron mobility of the doped sample is about 1.4 times that of the undoped sample. Also, doping improved the light absorption and photoluminescence efficiency. Additionally, the $I$–$V$ curve of the ZnO-doped WSe₂/Si heterojunction gradually changes from a rectification characteristic to a linear dependence, and the photocurrent increases by about four times when the light power increases from 0 to 25 mW/cm². Moreover, the heterojunction has a very high sensitivity to operating temperature; the current significantly increases as the temperature increases to $300^{\circ }$. With high absorptivity and photoluminescence efficiency, and sensitivity to light and temperature, ZnO-doped WSe₂ film is promising for use in optoelectronic devices.

A variational method is used to investigate the binding energies of bound polarons near the interface in a GaAs/Al_xGa_1-xAs heterojunction by considering the hydrostatic pressure effect. It is found that the comprehensive pressure effect on the heterojunction factors increases the binding energies near linearly. The pressure influence on the binding energy for the impurity located on the channel side is stronger than that for the impurity located on the barrier side. The pressure effect is more obvious when the impurity is located on the channel side and is not so far from the interface. The pressure influences on the longitudinal optical phonons and interface optical phonons are discussed.

Using density-functional theory (DFT) combined with non-equilibrium Green's function (NEGF), we have investigated the transport properties of carbon nanotubes with S–S, M–S, and M–M heterojunctions. The results show that the local states associated with topological defects arise at the junctions. The position and width of local states strongly depend on the configurations of the topological defects and their arrangement. The (7, 0)–(8, 0) and (8, 0)–(9, 0) heterojunctions present semiconducting characteristics. The (6, 0)–(9, 0) heterojunction maintains metallic properties. However, the 5/6/6/7 defects in the nanostructure decrease the electronic transport. More importantly, our results indicate that the I–V characteristics of the heterojunctions could be effectively controlled by gate voltage.

Two types of p–n junction were fabricated by depositing underdoped La_1.9Sr_0.1CuO₄ film and overdoped La_1.8Sr_0.2CuO₄ film on n-type 0.5 wt.% Nb-doped SrTiO₃ (NSTO) substrates using pulsed laser deposition technique (PLD), respectively. Current–voltage (I–V) characteristics of the La_2-xSr_xCuO₄/NSTO heterojunction were measured in the temperature range from 5 K to 300 K. All I–V curves show a fine rectifying property and a visible reduction of the diffusion potential (V_d) is observed, but the behaviors of V_d are vastly different for the underdoped and overdoped regimes at temperatures below T_c. Analysis results show that the characteristics of the heterojunction are possibly affected not only by the superconducting gap of LSCO at T_c, but also by the depletion layer in the interface of LSCO/NSTO junction. The variation of the depletion layer is possibly different under the same applied bias voltages for the underdoped La_1.9Sr_0.1CuO₄/NSTO junction and overdoped La_1.8Sr_0.2CuO₄/NSTO junction due to the difference of carrier density at La_1.9Sr_0.1CuO₄ and La_1.8Sr_0.2CuO₄.

In this paper, we studied the structural and electronic properties of core/shell nanocables composed of cubic silicon carbide nanowires (β-SiCNW) and boron nitride nanotubes (BNNT) using first-principles pseudopotential plane wave method within density functional theory. Our results show that the β-SiC/BNNT heterojunction structures are metallic, which primarily originates from the contributions of the BNNTs and the surfaces of SiCNWs. The BNNTs exhibit metallic characters after the SiC nanowires are inserted. The transition of the BNNTs is attributed to the charge transfer between BNNTs and SiCNWs.

This paper reports the temperature dependent electrical characterization of formyl-TIPPCu(II)/p-Si heterojunction diode which was fabricated by growing thin films of formyl-TIPPCu(II) on the p-type silicon substrate by thermal sublimation technique. The variation in electrical characteristics of the fabricated devices has been systematically investigated as the function of temperature by using current–voltage (I–V) measurements in the temperature range 299–339 K. The diode parameters like ideality factor, zero bias barrier height and parasitic series resistance have been found to be strongly temperature dependant. The zero bias barrier height increases while ideality factor and series resistance decreases with increasing temperature.

In this paper, copper-zinc-tin-sulfide (Cu₂ZnSnS₄) thin film was successfully fabricated by radio-frequency (RF) magnetron sputtering on glass substrate. The structural, optical and electrical properties of the film were studied by X-ray photoelectron spectroscopy (XPS), laser micro-Raman spectrometer, field emission scanning electron microscope (FESEM), UV-VIS spectrophotometer and Hall effect measurement, respectively. The results show that Cu₂ZnSnS₄ film is of good quality. A good nonlinear rectifying behavior is obtained for the GZO/Cu₂ZnSnS₄ heterojunction. Under reverse bias, high photocurrent is obtained.

Combining advanced transmission electron microscopy with high-precision first-principles calculations, the properties of Si(111)//6H-SiC(0001) (Si-terminated and C-terminated) heterojunction interface, such as work of adhesion, geometry property, electronic structure and bonding nature, are studied. The experiments have demonstrated that interfacial orientation relationships of Si(111)//6H-SiC(0001) heterojunction are $\mathrm{\text{Si[2-1-1]}}/\mathrm{\text{6H}}$-$\mathrm{\text{SiC}}[10\bar{1}0]$ and Si(111)/6H-SiC(0001). Compared with C-terminated interface, Si-terminated interface has higher adhesion and less relaxation extent.

For the disadvantages of conventional negative electron affinity (NEA) GaN photocathodes activated by Cs or Cs/O, new-type NEA GaN photocathodes with heterojunction surface dispensed with Cs activation are investigated based on first-principle study with density functional theory. Through the growth of an ultrathin $n$-type GaN cap layer on $p$-type GaN emission layer, a $p$–$n$ heterojunction is formed on the surface. According to the calculation results, it is found that Si atoms tend to replace Ga atoms to result in an $n$-type doped cap layer which contributes to the decreasing of work function. After the growth of $n$-type GaN cap layer, the atom structure near the $p$-type emission layer is changed while that away from the surface has no obvious variations. By analyzing the E-Mulliken charge distribution of emission surface with and without cap layer, it is found that the positive charge of Ga and Mg atoms in the emission layer decrease caused by the cap layer, while the negative charge of N atom increases. The conduction band moves downwards after the growth of cap layer. Si atom produces donor levels around the valence band maximum. The absorption coefficient of GaN emission layer decreases and the reflectivity increases caused by $n$-type GaN cap layer.

Two square steel columns are arranged in air to form two-dimensional square lattice phononic crystals (PNCs). Two PNCs can be combined into a non-orthogonal 45${}^{\circ }$ heterojunction when the difference in the directional band gaps of the two PNC types is utilized. The finite element method is used to calculate the acoustic band structure, the heterogeneous junction transmission characteristics, acoustic field distribution, and many others. Results show that a non-orthogonal PNC heterojunction can produce a multi-channel unidirectional transmission of acoustic waves. With the square scatterer rotated, the heterojunction can select a frequency band for unidirectional transmission performance. This capability is particularly useful for constructing acoustic diodes with wide-bands and high-efficiency unidirectional transmission characteristics.

The geometric structure, energy barrier and electronic properties of H-incorporated ${\mathrm{\text{Ti}}}_3{\mathrm{\text{SiC}}}_2/\mathrm{\text{Zr}}$ heterojunctions were investigated by first-principles calculations. Hydrogen atom settles in ${\mathrm{\text{Ti}}}_3{\mathrm{\text{SiC}}}_2/\mathrm{\text{Zr}}$ as interstitial impurity due to its small radius. Through calculating and analyzing the total energies of H-incorporated ${\mathrm{\text{Ti}}}_3{\mathrm{\text{SiC}}}_2/\mathrm{\text{Zr}}$ heterojunction, a much higher potential barrier (1.75 eV) was found when H atom diffuses from the interface into the ${\mathrm{\text{Ti}}}_3{\mathrm{\text{SiC}}}_2$ material than that (0.25 eV) into the Zr metal. The encountered potential barriers of H atom diffusing from vacuum into the ${\mathrm{\text{Ti}}}_3{\mathrm{\text{SiC}}}_2$ and Zr metal are also calculated, and they are both positive. These findings indicate that ${\mathrm{\text{Ti}}}_3{\mathrm{\text{SiC}}}_2$ is a suitable coating material to prevent the hydrogen embrittlement and corrosion in Zr metal. The electronic properties and valence bond properties of H-incorporated ${\mathrm{\text{Ti}}}_3{\mathrm{\text{SiC}}}_2/\mathrm{\text{Zr}}$ were analyzed based on the band structure, electronic density of states and Mulliken distribution. The calculated results show that all the H-incorporated ${\mathrm{\text{Ti}}}_3{\mathrm{\text{SiC}}}_2/\mathrm{\text{Zr}}$ heterojunctions exhibit metallic, covalent and ionic properties. These investigations may provide new insight into the underlying mechanisms of hydrogen diffusion in the ${\mathrm{\text{Ti}}}_3{\mathrm{\text{SiC}}}_2/\mathrm{\text{Zr}}$ heterojunction.