N-type Si Substrates Research Articles

Nanometer-thick TiO2 channel thin film transistors as radical monitors for plasma enhanced atomic layer deposition

Nanometer-thick-TiO2-channel thin-film transistors (TFTs) are examined as oxidizing-agent monitors for room-temperature atomic layer deposition (RTALD). RTALD is a plasma-based process using plasma-excited humidified argon where OH radicals oxidize the precursor-gas adsorbed surface. In the TFT, the anatase TiO2 channel, with a thickness of 16 nm, is attached to a 300 nm thick gate capacitor of SiO2, while the channel surface is exposed to the ALD ambient. A heavily doped n-type Si substrate attached to the gate SiO2 is used as the gate electrode. The gate width and length are 1000 and 60 μm, respectively. When the TFT is installed in the RTALD chamber, the drain-current waveform is recorded in the course of the metal organic gas adsorption, evacuation of the residual gas, oxidization, and evacuation. In the present study, three kinds of metal organic (MO) precursors, tetrakis(dimethyl)amino titanium, tris(dimethyl)amino silane, and trimethyl aluminum are examined. The drain current exhibits strong responses upon the exposure of the plasma excited humidified argon. This suggests that OH radicals in the plasma might oxidize the adsorbed MO precursors to produce the OH moieties, where the surface polarization of OH moieties might enhance channel conductivity. The experimental results suggest the applicability of the present TFT as a plasma monitor in RTALD.

Effect of HF and Ethanol Volume Ratio on Porous Silicon Formed by Photoelectrochemical Method on N-type Si(100) Substrates

Effect of HF and Ethanol Volume Ratio on Porous Silicon Formed by Photoelectrochemical Method on N-type Si(100) Substrates

Facile synthesis and characterization of Cu2Se thin films and self-powered p-Cu2Se/n-Si heterojunction with high-performance photoresponse

A facile, cost-effective, and scalable chemical vapor deposition technique was used to synthesize p-type Cu2Se thin films on glass and n-type Si substrates. Thorough characterization confirmed the films’ β-phase structure with the correct stoichiometric ratio and exceptional crystalline quality, exhibiting behavior akin to a degenerate semiconductor. Measurements unveiled a work function of 4.83 eV and a bandgap of 2.13 eV for Cu2Se. The fabrication of a p-Cu2Se/n-Si heterojunction was achieved by depositing the p-type Cu2Se thin film onto the n-type Si substrate. The resulting heterostructure displayed rectification behavior, and its energy band diagram resembled a Schottky diode. Further exploration into its photoelectric properties showcased the p-Cu2Se/n-Si heterostructure’s favorable self-powered attribute, characterized by fast, steady, reproducible, sensitive, and robust photoresponsive performance. Consequently, it proves highly suitable for applications in high-frequency photodetectors. Additionally, the p-Cu2Se/n-Si heterojunction’s photovoltaic power conversion efficiency exceeded the reported values of the CuO/Si and Cu2O/Si systems. Here, this study contributes significantly to the pivotal evaluation of p-Cu2Se/n-Si heterostructures for promising optoelectronic applications.

Laser ablation fingerprint in low crystalline carbon nanotubes: A structural and photothermal analysis

Carbon nanotubes (CNT) hold promise as photothermal materials due to their cost-effectiveness, stability, and broad optical absorbance. Here, we investigate the structural and morphological modifications in low-crystalline vertically aligned CNT synthetized via chemical vapor deposition on n-type Si substrates at 750 °C, followed by annealing treatment with near-infrared laser radiation. Raman spectroscopy revealed laser-induced amorphous regions, facilitating identification of ablation thresholds. Time-dependent nonlinear photothermal emission, associated with CNT ablation, showed a stable thermodynamic equilibrium with broad-band radiation from an electron-hole plasma. We propose a model based on Raman spectra and positional scans of the ablation fingerprint, enabling correlation with the beam temperature profile. This study offers insights into laser beam characterization, with potential applications in plasma and optics disciplines.

Investigating the impact of physical vapour deposition of palladium on electron-irradiated silicon substrates

This study reports on the effect of resistive physical vapour deposition of Pd Schottky contacts on the defects observed in an irradiated n-type Si substrate. Deep-level transient spectroscopy (DLTS) was used in order to investigate the possible defects in Schottky diodes on the n-type Si. In this study the defects present where the diode was deposited first and then irradiated (“post irradiated”) were compared to those present where the substrate was irradiated first, and the Pd deposited after irradiation (“pre-irradiated”). In the post-irradiated material, the familiar radiation-induced defects were observed. However, in the pre-irradiated material, fourteen new defects were observed, with DLTS signatures differing from those of the defects in the post-irradiated diodes. The newly identified defects seemed to be specifically caused by the deposition of Pd contacts after irradiation of the substrate, as these defects were not observed when other metals such as Au, Ni, Al and Ag were deposited after irradiation. In this paper, we will refer to the observed effect that Pd deposition replaced the familiar radiation-induced defects in Si with the new set of defects as the “Pd effect”. Careful experiments ruled out annealing due to inadvertent heating of the sample during deposition as a possible cause. Care was taken to avoid all sources of contamination: The effect was observed for different sources of Pd and crucibles. This effect was inhibited by the presence of a thin intermediate layer of Pd or Au deposited before irradiation. We therefore conclude that the effect is only observed when Pd is deposited directly onto the irradiated Si surface. Out of the fourteen newly observed defects, four defects, with activation energy of 182, 220, 360 and 607 meV, had DLTS signatures corresponding to those of defects previously observed in Pd-containing Si. For the rest of the defects, no defects with similar DLTS signatures were found in literature. We therefore believe that the defects observed are produced by defect enhanced diffusion of Pd. Overall, the study enhances our understanding of defect behaviour in silicon-based devices, particularly under irradiation and metal deposition conditions, and reveals the unique properties and effects of Pd.

Direct-Contact Seebeck-Driven Transverse Magneto-Thermoelectric Generation in Magnetic/Thermoelectric Bilayers.

Transverse thermoelectric generation converts temperature gradient in one direction into an electric field perpendicular to that direction and is expected to be a promising alternative in creating simple-structured thermoelectric modules that can avoid the challenging problems facing traditional Seebeck-effect-based modules. Recently, large transverse thermopower has been observed in closed circuits consisting of magnetic and thermoelectric materials, called the Seebeck-driven transverse magneto-thermoelectric generation (STTG). However, the closed-circuit structure complicates its broad applications. Here, STTG is realized in the simplest way to combine magnetic and thermoelectric materials, namely, by stacking a magnetic layer and a thermoelectric layer together to form a bilayer. The transverse thermopower is predicted to vary with changing layer thicknesses and peaks at a much larger value under an optimal thickness ratio. This behavior is verified in the experiment, through a series of samples prepared by depositing Fe-Ga alloy thin films of various thicknesses onto n-type Si substrates. The measured transverse thermopower reaches 15.2 ± 0.4µVK-1, which is a fivefold increase from that of Fe-Ga alloy and much larger than the current room temperature record observed in Weyl semimetal Co2MnGa. The findings highlight the potential of combining magnetic and thermoelectric materials for transverse thermoelectric applications.

Influence of the substrate conductivity type on the electroluminescence properties of PP+IN and PIN+N diodes based on amorphous silicon carbide (a-Si1-xCx:H) / crystalline silicon (c-Si) heterostructures

The study of the conduction and light emission mechanisms of PIN diodes based on amorphous silicon-carbide (a-Si1-xCx:H) thin film and crystalline silicon (c-Si) substrates is reported in this work. Using the same low-temperature process (200 °C), PP+IN and PIN+N structures were fabricated on p-type and n-type silicon (Si) substrates, respectively. The plasma enhanced chemical vapor deposition (PECVD) technique was employed for the active layers deposition where two different CH4/SiH4 flow rates ratios of 30 sccm/6 sccm and 30 sccm/1 sccm were used. All structures show red-orange light emission in forward bias (FB). The structures with the active layer deposited with a lower SiH4 flow rate, display light emission with a higher intensity at a lower voltage bias.In addition, we related the current-voltage measurements with different conduction models and the dominant charge transport mechanisms in the PIN structures were proposed. The highest Si content structures were related to Fowler-Nordheim (F-N) tunneling, because of its active layer with lower barrier height. On the other hand, the lowest Si content structures were associated with the Poole-Frenkel (P-F) emission, due to a higher density of defects in localized tail states. The results showed the same conduction and emission mechanisms for the PP+IN and PIN+N diodes with the same active layer, regardless of the conduction type of substrate, proving that it is feasible to use the same process for developing light emission devices on p-type and n-type Si substrates.

Semi-conductive carbon from industrial tea waste biomass for a p-n junction

AbstractSome semiconducting carbonaceous material was developed from industrial tea waste biomass by catalytic pyrolysis and heteroatom doping; then, a p-n junction was realized on an n-type Si substrate. I-V characteristics of the structures revealed that each structure had a different reverse saturation current, ideality factor, cut-in voltage and series resistance. The variations in the characteristics are attributed to the amorphous and non-uniform nature of the carbonaceous material. Due to the high resistivity of the carbonaceous material, a significant amount of series resistance was present in the characteristics, resulting in very small levels of current that would inhibit the practical use of the structure as a semiconductor diode in electronic circuits.

Co-deposition of CuO:ZnO Nanocomposite on n-Type Si Substrate by Chemical Bath Deposition (CBD) Technique for Photovoltaic Application

Co-deposition of CuO:ZnO Nanocomposite on n-Type Si Substrate by Chemical Bath Deposition (CBD) Technique for Photovoltaic Application

The dopant (n- and p-type)-, band gap-, size- and stress-dependent field electron emission of silicon nanowires.

This study investigates the electron field emission (EFE) of vertical silicon nanowires (Si NWs) fabricated on n-type Si (100) and p-type Si (100) substrates using catalyst-induced etching (CIE). The impact of dopant types (n- and p-types), optical energy gap, crystallite size and stress on EFE parameters has been explored in detail. The surface morphology of grown SiNWs has been characterized by field emission scanning electron microscopy (FESEM), showing vertical, well aligned SiNWs. Optical absorption and Raman spectroscopy confirmed the presence of the quantum confinement (QC) effect. The EFE performance of the grown nanowire arrays has been examined through recorded J-E measurements under the Fowler-Nordheim framework. The Si NWs grown on p-type Si showed a minimum turn-on field and also a higher field enhancement factor. The band-bending diagram also suggests a lower barrier height of p-type Si NWs compared to n-type Si NWs, which plays a key role in enhancing the EFE performance. These investigations suggest that dopant types (n- and p-types), band gap, crystallite size and stress influence the EFE parameters and Si NWs grown on p-type Si (100) substrates are much more favorable for the investigation of EFE properties.

Concurrent Thermal Reduction and Boron-Doped Graphene Oxide by Metal–Organic Chemical Vapor Deposition for Ultraviolet Sensing Application

We synthesized a boron-doped reduced graphene oxide (BrGO) material characterized by various electrical properties, through simultaneous thermal reduction and doping procedures, using a metal–organic chemical vapor deposition technique. X-ray photoelectron spectroscopy (XPS) was used to study the impact of the doping level on the B bonding in the reduced graphene oxide (rGO) layer that is influenced by the annealing temperature. The synthesized BrGO layer demonstrated a high B concentration with a considerable number of O-B bonds, that were altered by annealing temperatures. This resulted in a decreased work function and the formation of a Schottky contact between the BrGO and n-type Si substrate. Due to the higher proportion of B-C and B-C3 bonding in the BrGO/Si device than that in the rGO/Si, the decreased Schottky barrier height of the BrGO/n-Si vertical junction photodetector resulted in a higher responsivity. This study showcases a promise of a simple B-doping method in use to alter the electrical characteristics of graphene materials.

The effect of the isoelectronic traps on the luminescence properties of Zn1-XCdXO thin films

In this report, Zn1-xCdxO ceramic thin films were deposited by the sol-gel method on an n-type Si (100) substrate. The structure, morphology, and luminescence properties of the thin films were studied. To elucidate the structure and the optical properties of Zn1-xCdxO thin films, our study focuses on the roles of changing the content of the doped Cd and the annealing temperature in Cd-doped ZnO thin films. The Cd doping behavior was investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and photoluminescence (PL). The research concentrates on the effects of doping concentration, annealing temperature, and isoelectronic trapping on the crystallization quality and luminescence properties of the thin films. On the basis of the different electronegativity of the doping elements, Cd substitution for Zn forms isoelectronic traps, which influence the intensity of luminescence and change the luminous peaks. By raising the annealing temperature further, the intensity of each diffraction peak of ZnO is gradually increasing, improving the quantity of Cd entering the ZnO crystal lattice. The PL spectra display that the ZnO thin films only appear in yellow-green emission bands, which appear redshift through the incorporation of Cd. With the increase in Cd doping amount, the yellow light luminous center keeps moving in the low energy direction. When the Cd doping amount reaches 20 %, the luminescence intensity reaches its maximum, which holds great promise for its application in light devices.

Low-temperature growth of Ga2O3 thin films on Si substrates by metal organic chemical vapor deposition and their electrical characteristics

In this paper, Ga2O3 thin films were grown on n-type Si substrates at various growth temperatures of 500, 550, 600, 650, and 700 °C. The Ga2O3 thin films grown at 500 and 550 °C were characterized by featureless flat surfaces. Films grown at higher temperatures of 600, 650, and 700 °C showed a very rough surface morphology. To determine the effect of annealing on the thin films grown at relatively low temperatures (500, 550, 600, 650, and 700 °C), the Ga2O3 films were thermally treated at 900 °C for 10 min. The crystal structure of the Ga2O3 films grown at 500 and 550 °C changed from amorphous to polycrystalline with a flat surface. The Ga2O3 film grown at 550 °C was chosen for the fabrication of a Schottky barrier diode, whose electrical properties were evaluated before and after thermal treatment. A metal–semiconductor–metal-type photodetector was fabricated using a Ga2O3 thin film grown at low temperatures, whose photocurrent under 266-nm UV illumination wavelength was 5.32 times higher than the dark current under an operating voltage of 10 V.

Versatility Investigation of Grown Titanium Dioxide Nanoparticles and Their Comparative Charge Storage for Memristor Devices.

Memristive devices have garnered significant attention in the field of electronics over the past few decades. The reason behind this immense interest lies in the ubiquitous nature of memristive dynamics within nanoscale devices, offering the potential for revolutionary applications. These applications span from energy-efficient memories to the development of physical neural networks and neuromorphic computing platforms. In this research article, the angle toppling technique (ATT) was employed to fabricate titanium dioxide (TiO2) nanoparticles with an estimated size of around 10 nm. The nanoparticles were deposited onto a 50 nm SiOx thin film (TF), which was situated on an n-type Si substrate. Subsequently, the samples underwent annealing processes at temperatures of 550 °C and 950 °C. The structural studies of the sample were done by field emission gun-scanning electron microscope (FEG-SEM) (JEOL, JSM-7600F). The as-fabricated sample exhibited noticeable clusters of nanoparticles, which were less prominent in the samples annealed at 550 °C and 950 °C. The element composition revealed the presence of titanium (Ti), oxygen (O2), and silicon (Si) from the substrate within the samples. X-ray diffraction (XRD) analysis revealed that the as-fabricated sample predominantly consisted of the rutile phase. The comparative studies of charge storage and endurance measurements of as-deposited, 550 °C, and 950 °C annealed devices were carried out, where as-grown device showed promising responses towards brain computing applications. Furthermore, the teaching-learning-based optimization (TLBO) technique was used to conduct further comparisons of results.

The impact of oxygen partial pressure in modifying energy storage property of lanthanum doped multiferroic bismuth ferrite thin films deposited via pulsed laser deposition

Lead-free dielectric thin films' potential as pulse capacitors in power electronic devices has garnered attention to their energy storage usage. The current study aims at the growth of multiferroic thin films using the pulsed laser deposition technique for energy storage capacitor applications. Under various OPPs, single-phase La-doped bismuth ferrite (Bi0.993La0.007FeO3) BLFO thin film of 200 nm thickness is deposited on quartz and n-type Si substrates (15 to 30 SCCM). The crystal planes (110) and (006) of the rhombohedral phase with space group R3c are confirmed by high-resolution HRTEM and SAED patterns that augmented the XRD analysis. The optimized films have a smooth, uniform microstructure with 3 nm root-mean-square (RMS) roughness. The film shows an enhanced dielectric constant of 447 at room temperature with an improved ferroelectric property. At 488 kV/cm, the 20 SCCM BLFO films achieved 78.42 % energy efficiency and 2.09 J/cm3 energy density. The same films also exhibited a lower value of bandgap energy, confirming the strong absorption at 452 nm wavelength. The relatively high refractive index of 2.78 is determined for the same film suggesting the higher crystallinity of the film. Further, the low magnitude of leakage current density of the grown film is ∼10−7 A/cm2 at ±100 kV/cm. Though achieving the pure phase and fabricating BLFO thin films is challenging, these results are appropriate for the thin films to realize as energy storage capacitor applications.

Enhanced magnetic properties and leakage current mechanism in bismuth lanthanum ferrite thin films coupled with impedance and magnetic studies

A highly crystalline and pure phase Bi0.993La0.007FeO3 (BLFO) thin films have been grown using a pulsed laser deposition technique. The structural analysis confirmed the thin film is well crystallized with a rhombohedral crystal structure with an R3c space group. The BLFO phase and composition are also confirmed by transmission electron microscopy and EDAX analysis. The surface chemistry of thin films, analysed by X-ray photon spectroscopy, reveals Fe's presence in Fe3+ and Fe2+ states. At RT, the deposited film exhibited high dielectric permittivity (∼4 × 102) and low dielectric loss (∼10−1). The isothermal magnetization on highly oriented (001)-MgO and LaAlO3 (LAO) substrates is investigated. The response is compared to the randomly oriented polycrystalline films on low-cost substrates (Pt/TiO2/SiO2/Si and n-type Si substrate). The enhanced saturation magnetization of 57 emu/cm3 and 36 emu/cm3 at 10 K and 300 K are observed at 2.5 kOe applied field for the film grown on the LAO substrate. Additionally, the low leakage current density of the film is obtained around ∼1 × 10−7 A/cm2 at a field of 100 kV/cm. Acquiring single-phase BLFO thin films with enhanced electrical and magnetic properties can be relevant in designing multiferroic materials for multiple-state memories, magnetic field sensors, and spintronics applications.

Nonvolatile resistive switching in lead-free La2CoMnO6-based memory device

Dense and flat La2CoMnO6 films as the resistive switching functional layer were deposited on n-type Si substrates by sol–gel method. Excellent bipolar resistive switching performance was observed in the Au/La2CoMnO6/Si device for the first time. The high and low resistance states with a ratio of ∼105 could be maintained for more than 1.4 × 104 s and 750 cycles without significant degradation at room temperature. The bipolar resistive switching effect could be sustained within a wide temperature range of 220 K∼300 K. Electrical conduction analysis indicated that the resistive switching behavior in La2CoMnO6 films was primarily controlled by space-charge-limited current mechanism which originated from the change of oxygen vacancies. Density functional theory calculations indicated that the conductive ability of La2CoMnO6 films was promoted with increasing concentration of oxygen vacancies. Moreover, it is found that the modulation of the barrier located at the Au/La2CoMnO6 interface was responsible for the resistive switching under applied bias voltages.

INVESTIGATION OF STRUCTURAL, OPTICAL, AND ELECTRICAL PROPERTIES OF ITO FILMS DEPOSITED AT DIFFERENT PLASMA POWERS: ENHANCED PERFORMANCE AND EFFICIENCY IN SHJ SOLAR CELLS

This article presents an investigation into the structural, optical, and electrical properties of Indium Tin Oxide (ITO) films that were deposited utilizing various plasma powers. The transmittance values in the visible region were measured, revealing that the ITO film deposited at 2050 W exhibited the highest transmittance (81%). Additionally, the sheet resistance values of all films were analyzed, indicating that the ITO film deposited at 2050 W had the lowest sheet resistance (64.9 Ω/sq). By means of XRD analysis, the structural properties of the films were meticulously scrutinized, and the distinctive diffraction peaks associated with the ITO films were successfully identified. Notably, the ITO film deposited at 2050 W demonstrated superior performance compared to the other films deposited using various plasma powers. Finally, we report a noteworthy efficiency of 17.03% achieved in the SHJ solar cell fabricated with the ITO film deposited at 2050 W on a 5x5 cm2 n-type Si substrate.

Effect of Annealing Temperature on the Structure and Properties of La2O3 High-K Gate Dielectric Films Prepared by the Sol-Gel Method

This article presents the sol-gel method for depositing La2O3 thin films on n-type Si substrates and quartz substrates, and investigates the impact of annealing temperature on the microcomposition, surface morphology, optical properties, and band characteristics of the films. X-ray diffraction (XRD) analysis indicates that the films are amorphous below 500 °C, with annealing resulting in a hexagonal-phase La2O3 (h-a2O3) and new non-hydrated impurities. Fourier-transform infrared (FTIR) analysis reveals that the prepared La2O3 film is unaffected by moisture. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) provide evidence that the La2O3 film has a smooth, uniform surface without cracks. The roughness increases from 0.426 nm to 1.200 nm, and the film thins from 54.85 nm to 49.80 nm as the annealing temperature rises. The film’s transmittance is above 75%, as measured by UV-Vis, and the calculated optical bandgap increases from 5.11 eV to 5.75 eV. The calculated band offset of the La2O3 film is greater than 1 eV, which meets the minimum requirements for MOS devices, thus providing promising prospects for La2O3 films in MOS applications.

Thermoelectric performance of Fe2V0.9W0.1Al thin films deposited on n-type Si substrates

Fe2V0.9W0.1Al thin films are prepared on n-type Si substrates by means of rf magnetron sputtering with varied substrate temperatures from 743–1043 K, then subsequently annealed for one hour in a vacuum at 1043 K. The thin films deposited at 1043 K are chemically degraded, exhibiting a low Seebeck coefficient, –65 μV K–1, at 330 K. On the other hand, the films deposited at 943 K possess –100 μV K–1 in a Seebeck coefficient at around 330–350 K, which is very similar to the Seebeck coefficient of the bulk W-substituted Fe2VAl that possesses a well-ordered L21 structure. The maximum power factor of 1.6 mWm–1 K–2 was obtained for the sample deposited at 943 K. Accordingly, with the thermal conductivity of 3.5 Wm−1 K−1, the figure of merit reached up to ZT = 0.16, which is comparable with Fe2V0.9W0.1Al of bulks and two times larger than that of the thin films of Si-substituted Fe2VAl.