Semiconductor Materials Research Articles

Calculation of Curie Temperature and Carriers Effective Masses of (Ga, Mn)As Diluted Magnetic Semiconductor from the Eight-Band k.p Model

An important step toward the development of spintronic information processing, transfer, and storage devices is the discovery of a dilute magnetic semiconductor (DMS) that demonstrates carrier-mediated ferromagnetism and maintains its magnetic properties above room temperature. Despite considerable progress made in recent decades, the maximum Curie temperature (∼200 K) remains well below room temperature. Mndoped GaAs are among the various diluted magnetic semiconductor materials that have been studied and have emerged as one of the most promising contenders for technological usage. The key characteristic of GaMnAs is its ferromagnetic properties, which are critical for spintronic devices. The primary goal of this work is to compute two critical properties of GaMnAs: the effective masses and the Curie temperature. The 8-band k.p model put forth by Kane was utilized to compile the GaMnAs band parameters using a MATLAB program. Our calculations are based on Lowdin perturbation theory, where spin-orbit, sp-d exchange interaction, and biaxial strain are taken into account. We calculated the Curie temperature of the GaMnAs alloy, within the mean-field approach based on the Zener model. Our findings demonstrated a direct proportionality relationship between the Curie temperature and the hole concentration (p) in GaMnAs. Moreover, we looked into how the Mn content and strain affected the effective masses of electrons, heavy, and light holes that were calculated for various crystallographic directions in GaMnAs. The effective masses that were calculated were highly dependent on the Mn content, which ranged from 1% to 5%, and the strain, which varied from −2% (tensile strain) to 2% (compressive strain).

Optical and optoelectrical characterizations of Cu2ZnSn3S8: A potential nominee for optoelectronic and photovoltaic applications

A successful trial has been accomplished in synthesizing a stable phase of Cu2ZnSn3S8 (CZTS8). The deposited thin films have been obtained by utilizing the chemical bath deposition (CBD) process. Basic characterizations have been applied to check the formation of our new stable material. The formed CZTS8 films disclose the amorphous nature as presented in the x-ray diffraction (XRD) patterns. Also, an enhancement in film morphology has been obtained by expanding the film thickness. Moreover, optoelectrical and linear/nonlinear optical features have been studied for the as-deposited films. Our material has interesting characteristics to be a promising window sheet for thin film solar cells. It reveals a tendency to be an n-type semiconductor material. Further, it shows high optical absorption as well as high optical conductivity. Moreover, it has a direct optical transition, and its energy gap is varied in the range (3.89 eV - 3.94 eV). Additionally, the dispersion and optoelectrical indices were affected by the variation in both film thickness and film roughness. Furthermore, the nonlinear optical indices χ(1),χ(3) and n2 were improved via the increase in film thickness. A satisfactory correlation has been performed between all of the evaluated parameters. The main goal of this study has been achieved by obtaining n-type material by increasing the Tin and Sulfur contents in the CZTS8 as compared with the known p-type material (Cu2ZnSnS4) CZTS4. The revealed findings acknowledge that CZTS8 could be a promising nominee for either optoelectronic or photovoltaic applications.

Nano-structured urchin-like photothermal covalent organic frameworks for efficient Solar-Driven interfacial water evaporation

Solar-driven interfacial water evaporation is a promising sustainable technology to alleviate the global energy crisis and clean water shortage. The design of advanced photothermal materials play the critical role to utilize photothermal heat for water evaporation. Covalent organic frameworks (COFs) as a new class of crystalline porous polymer semiconductor materials have been deemed as an ideal nanoscale platform for designing photothermal materials with notable features like highly ordered structures, porous open channels, and tunable structure and functionality. In this work, we focus on the regulation of the multi-scale structure of COFs and design hierarchically nano-structured photothermal COFs for efficient solar-driven interfacial water evaporation. At the molecular scale, we synthesize a photothermal functionalized COF-366-OH using photosensitive 5,10,15,20-tetrakis(4-aminophenyl) porphyrin (TAPP) and 2,5-dihydroxyterephthalaldehyde (DHTA) as building blocks. At the micro-nano scale, we introduce the π-conjugated catechol molecule 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) to regulate COF polycondensation and assembly, which enable the shaping of COF-366-OH into urchin-like nano-morphologies (namely UCOF-366-OH). The synthesized UCOF-366-OH exhibits high crystallinity, large surface area, excellent photothermal conversion capacity, and strong hydrophilicity. Furthermore, UCOF-366-OH is processed into a photothermal composite membrane. With localized solar heating and optimized water transport at the water evaporation interface, a high evaporation rate of 2.51 kg m−2h−1 with solar-to-vapor efficiency of 97.3 % is achieved. This work paves a new way for the multi-scale structural design of COF-based photothermal materials and highlights their innovative application in solar water evaporation.

Revealing the Effect of Ionic Traps on Photovoltaic Performance of Organic Semiconductor Materials

Revealing the Effect of Ionic Traps on Photovoltaic Performance of Organic Semiconductor Materials

Progress of joint process research on purification of high purity quartz sand

High-purity quartz sand is an important raw material for semiconductors, photovoltaics, aerospace and other cutting-edge fields, high-quality natural crystals can no longer meet the urgent demand for high-purity quartz in the domestic market, and it is imperative to accelerate the realisation of high-quality quartz purification technology from non-quality mineral sources. This paper summarises the joint process flow in the unused scenario, and outlines the main methods for the purification of quartz sand in China at present, including pretreatment, ultrasound-assisted leaching, chlorination roasting, etc., from the point of view of the joint process, and puts forward the problems that exist in these methods, so as to provide certain references for the research on the purification process of high-purity quartz sand in China.

Hexagonal ZnTiO3 single-crystalline films on α-Al2O3 substrates: Structural and photoelectric properties

Hexagonal ZnTiO3 (h-ZnTiO3) films with stoichiometric were deposited on α-Al2O3 substrates using pulsed laser deposition (PLD) method and post annealing process. The effect of oxygen partial pressure on Zn/Ti atomic ratio, as well as the influence of annealing treatment on the structural and optical properties of the films were investigated in detail. The optimum h-ZnTiO3 film was deposited under 5 Pa oxygen partial pressure and annealed at 800°C, and it exhibited excellent crystalline quality and an optical band gap of 3.72 eV. A photodetector based on the film was fabricated, and its photoresponsivity was approximately 0.18 mA/W under 308 nm ultraviolet light irradiation. This demonstrates that as a wide bandgap semiconductor material, h-ZnTiO3 has potential applications in the field of devices.

Study of Chemical-Physical Cleaning Technologies for Better Particle Removal Trapped on the Crystal Defects of 4H-SiC

Silicon carbide (SiC) stands out as a superior power semiconductor material due to its exceptional physical properties. However, conventional RCA cleaning methods are ineffective for SiC wafers. This study evaluates the efficacy of chemical-mechanical cleaning techniques, specifically PVA brush scrubbing and megasonic cleaning with hydrogen dissolved deionized water (DIW), in removing particle contaminants from SiC wafers. Findings reveal that while both methods effectively clean the wafer surface, megasonic cleaning with hydrogen dissolved DIW excels in removing particles trapped in crystal defects due to enhanced bubble cavitation. Thus, it is recommended for optimal SiC wafer cleaning.

Synthesis of novel Fe-BiOCl based nanosheets assembled rod (FBC-NSR)-based photoactive materials: an effective photodegradation of antibiotics

Fe-incorporated BiOCl-nanosheet assembled rods (FBC-NSR) based photoactive materials were synthesized using a simple sol–gel process to degrade tetracycline (TC) pharmaceuticals compound (PCs) under solar irradiation. The as-prepared FBC-NSR-based photoactive materials were characterized using various characterization techniques including scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), photoluminescent (PL) spectroscopic analysis, and Fourier transform infrared spectroscopy (FT-IR). The structural changes were observed upon doping of Fe metals within the FBC-NSR-based photoactive materials. Intriguingly, the band gap value decreased from ~ 1.81 eV to ~ 1.29 eV with increasing the amount of Fe metals (0.5 g, and 1.0 g) within the FBC-NSR named as FBC-NSR-2 and FBC-NSR-3-based photoactive materials, respectively. The lower band gap value favors the photodegradation of environmental pollution. The synthesized FBC-NSR-3 shows the highest degradation ~ 97% and ~ 72.1% at 1 mg/L and 10 mg/L TC antibiotic, respectively. The photodegradation was higher at pH 10, indicating •OH radicals play a major role in the photodegradation of TC molecules. PL spectra confirm the higher oxygen vacancy, improved transfer of electrons, and separation efficiency of photo-induced electron hole-pairs, thereby high photodegradation efficiency. Therefore, the preparation of FBC-NSR-based photoactive materials is simple, cost-effective, and promising semiconductor materials for the removal of environmental pollution.

Light Emission of Sn/Ge MQW pin Diodes on Si

Sn/Ge multi-quantum well diodes integrated on Si were grown pseudomorphically on Ge virtual substrates on Si using molecular beam epitaxy. Temperature-dependent electroluminescence analyses were conducted on these devices across a range of temperatures, from 290 K to 12 K. This analysis identified four distinct energy transitions across the entire temperature range. Two of the peaks were observed at high temperatures and were no longer discernible as the temperature decreased. The remaining two peaks were only measured at low temperatures. By analyzing them with a Ge reference diode, one of the peaks was identified as a defect peak. The intensity of the other peak increased as the temperature decreased, which is consistent with the behavior of a direct transition in an indirect semiconductor material.

(Invited) Selective Wet Etching of Semiconductor Materials by Novel Catalyst-assisted Modes

Since reports in the mid-1990s on metal-induced pitting on a Si surface in microelectronics, much attention has been paid to the positive use of corrosion of a semiconductor surface loaded with a metallic catalyst in solutions, known as metal-assisted chemical etching. This paper describes two novel modes of catalyst-assisted etching. The first involves the formation of nano trenches along the atomic step edges of a Si(111) surface with the help of self-assembled metallic nanowires, enabling the separation of neighboring terraces. The second discusses the science and application of nanocarbon-assisted etching, free from noble metals, of a Ge surface in water.

Reaxff MD Analysis of Substrate Material Properties into Oxide Films during Thermal Oxidation Process of Group IV Semiconductor Materials

Oxide films used in semiconductor devices have attracted much attention because they can protect substrate surfaces from impurities and suppress current loss. In recent years, there have been growing expectations for oxide film formation on Ge substrate materials, which have a uniquely high hole mobility among group IV semiconductor materials. We have investigated an efficient oxide film formation method using reactive molecular dynamics (ReaxFF MD) simulation. We focused on dissociation, the initial step of oxidation, and confirmed how easily dissociation occurs. To search for conditions that promote dissociation, we checked the dangling bound density and adsorption angle on the substrate surface. The wider space between dimers on the Ge substrate may result in a shallower O2 adsorption angle. This increases the dissociation rate because each of the two O2 atoms is more likely to bond to the substrate.

Atomistic study of selenium doping effects on the mechanical properties of zinc-blende and wurtzite CdTe nanowires

CdSexTe1–x semiconductor materials, having potential to be used to design dependable and reproducible nanowire devices, require an extensive study of their mechanical behaviors. The uniaxial tensile deformation mechanism of CdSexTe1–x nanowires (NWs) with different Se dopant concentration are yet to be explored. By integrating theoretical analysis with computational simulation, this research demonstrated that Se doping in CdTe NWs influences the mechanical response and failure modes. Ultimate tensile strength (UTS) and elastic modulus (EM) were studied for both zinc-blende (ZB) and wurtzite (WZ) structures with different crystal orientations. The findings revealed that these mechanical properties increase linearly with increasing Se concentration in all cases. In addition, the WZ structures exhibited similar mechanical properties under both zigzag and armchair loadings, unlike the ZB structures, which exhibited a strong dependence on the crystal orientation. The [111]-oriented ZB structures showed the highest EM and UTS whereas [100]-oriented ZB structures showed lowest EM and UTS. The failure mechanism was explored for CdSe50Te50 to underscore the influence of the dopant on the NWs failure for tensile loading. In both the cases of WZ structure, the failure planes were perpendicular to the loading direction. Furthermore, the failure plane varied with the Se content in ZB CdSexTe1–x. Atomic coordination and bond length affected by doping defined the alterations of mechanical properties and the preferred modes of failure. The significance of the interaction between doping elements and nanowire structures offers insights that unite material science and mechanics, contributing to the scientific understanding of solid materials’ behavior.

Efficient photocatalytic CO2 and Cr(VI) reduction on carbon quantum dots/carbon nitride heterojunctions

Carbon quantum dots (CQDs), known for their exceptional optical properties, hold the potential to enhance light absorption, charges separation and transfer in semiconductor materials. However, using cheap medicinal materials as precursors in the field of photocatalysis to obtain CQDs has seldom concerned. In this study, we utilized biomass-derived CQDs from carbon-rich licorice powder to improve photocatalytic CO2 and Cr(VI) reduction in polymer carbon nitride (PCN). The CQDs/g-C3N4 heterojunctions were synthesized via a hydrothermal method, and the successful fabrication and integration of CQDs on g-C3N4 surfaces were confirmed through detailed characterization. The optimal sample with a licorice powder to PCN mass ratio of 0.05:1 ((50CQDs/CN) demonstrates a tripling in CO2 conversion efficiency under simulated sunlight compared to the reference PCN. Under visible light irradiation, the 50CQDs/CN also performs superior photocatalytic Cr (VI) removal efficiency, which is 2.48 times of that of the reference PCN. This significant boost is attributable to the successful construction of the CQDs/CN heterojunction and the abundance of functional groups on the CQDs surface, which provide more active sites, improve light absorption and increase charges migration rates. The stability of these new photocatalysts was confirmed through repeated photocatalytic cycles, indicating their potential for practical applications. Mechanistic studies reveal insights into the enhanced photocatalytic pathways and intermediate conversion processes. Our findings present a novel, efficient and sustainable route to fabricate g-C3N4-based photocatalysts, offering a promising strategy for further mitigate the greenhouse gas crisis and environmental pollution.

Negative photoconductance in NiO/B-rGO nanocomposite-based UV photodetector: Structural and Photoelectric properties

The manifestation of uncommon negative photoconductance (NPC) in semiconductor materials has recently emerged as a significant breakthrough in various research applications. Despite its potential, nickel oxide (NiO), a transition metal oxide, has not been extensively explored in optoelectronic applications. However, when combined with carbon materials such as graphene oxide (GO), NiO demonstrates considerable promise. Additionally, doping GO with acceptor atoms like boron can modify its electronic behavior and enhance its functionality. In this study, we present a straightforward synthesis and preparation method for NiO/B-rGO nanocomposite, followed by their integration into UV photodetector devices. We investigate their structural and morphological characteristics using various analytical techniques. Furthermore, electrical characterization via I–V curve analysis is conducted to assess their photoresponse and reveal their photoconductance behavior. The results highlight negative photoconductance (NPC) under UV photoexcitation compared to the dark case, with this behavior is attributed to the trapping and recombination processes of carriers, which is thoroughly discussed, and supported by electrical noise evaluation. Additionally, the performance of the NiO/B-rGO device demonstrates superior photoresponse, with a responsivity of 0.92 A/W and a detectivity of 1.38 × 101⁰ Jones at low reverse bias.

Green and regulable synthesis of CdNCN on CdS semiconductor: Atomic-level heterostructures for enhanced photocatalytic hydrogen evolution

In the realm of photoenergy conversion, the scarcity of efficient light-driven semiconductors poses a significant obstacle to the advancement of photocatalysis, highlighting the critical need for researchers to explore novel semiconductor materials. Herein, we present the inaugural synthesis of a novel semiconductor, CdNCN, under mild conditions, while shedding light on its formation mechanism. By effectively harnessing the [NCN]2⁻ moiety in the thiourea process, we successfully achieve the one-pot synthesis of CdNCN-CdS heterostructure photocatalysts. Notably, the optimal CdNCN-CdS sample demonstrates a hydrogen evolution rate of 14.7 ​mmol ​g−1 ​h−1 under visible light irradiation, establishing itself as the most efficient catalyst among all reported CdS-based composites without any cocatalysts. This outstanding hydrogen evolution performance of CdNCN-CdS primarily arises from two key factors: i) the establishment of an atomic-level N-Cd-S heterostructure at the interface between CdNCN and CdS, which facilitating highly efficient electron transfer; ii) the directed transfer of electrons to the (110) crystal plane of CdNCN, promoting optimal hydrogen adsorption and active participation in the hydrogen evolution reaction. This study provides a new method for synthesizing CdNCN materials and offers insights into the design and preparation of innovative atomic-level composite semiconductor photocatalysts.

Investigation of Spintronic Properties of Transition Metal Doped ZnO Thin Films Produced by Sol-Gel Spin Coating

Transition metal-doped diluted semiconductor materials have attracted significant interest in spintronic applications. In order to investigate the structural, optical, electrochemical, and magnetic properties of these diluted magnetic semiconductors, transition metal-doped ZnO thin films were successfully produced at room temperature using a low-cost sol-gel spin coating technique with the same molar ratios. XRD analyses revealed that all samples adopted the crystal structure of ZnO. Optical measurements indicated high transparency in the visible region for all samples, while electrical measurements confirmed that all samples were n-type semiconductors. Finally, magnetic measurements showed that pure ZnO and Al-doped ZnO exhibited diamagnetic behavior, while Ni and Co doped ZnO displayed magnetic behavior. These results show that Co and Ni-doped ZnO films can be used as diluted magnetic semiconductor materials in spintronic applications.

Inkjet-printed p-type tellurene and n-type MoS2 transistors for CMOS electronics

Abstract Two-dimensional semiconductor materials combine exceptional electronic transport properties with mechanical flexibility and hence can be an ideal choice for large-area flexible and wearable electronics. While inkjet printing may be a suitable approach to fabricate high throughput electronic components on polymer substrates, solution-processed 2D semiconductor network transistors suffer from two major hindrances: extremely high inter-flake resistance and the lack of high-performance p-type semiconductors. This study shows that inkjet-printed tellurium nanowires or tellurene nanoflakes can offer high-performance p-type TFTs with current density up to 100 μA/μm and an On-Off ratio >105. In order to circumvent the high inter-flake junction resistance, a narrow-channel, near-vertical device architecture has been used that ensures predominantly intra-flake/ intra-nanowire transport, which resulted in three orders of magnitude increase in the current density compared to conventional devices without compromising on the On-Off ratio. Moreover, we show the whole device operation within ± 2 V, with a threshold voltage close to 0 V. The complete device fabrication is carried out at room temperature, thereby making it compatible with inexpensive polymer substrates. Next, outstanding device performance has also been realized with electrochemically-exfoliated and inkjet-printed n-type MoS2 TFTs, demonstrating a current density of 60 μA/μm and an On-Off ratio of 106. Furthermore, we show tellurene-based p-type depletion-load unipolar inverters and CMOS inverters alongside n-type MoS2 TFTs, demonstrating a signal gain of 12 and 11, respectively. The CMOS inverters are found to operate at a frequency of 1 kHz.

Structural Stability of Mixed‐Halide Perovskite Nanocrystals in Energy Storage: The Role of Iodine Expulsion

AbstractIn the pursuit of efficient optoelectronics devices, hybrid lead halide perovskite quantum dots (PQDs) have emerged as highly promising semiconductor materials due to their intriguing properties. While these materials have been used in many applications, the fundamental understanding of their behavior remains relatively unexplored, especially for the mixed halide perovskite samples. To facilitate the advancement of PQD technologies for commercial applications, it is essential to gain insights into the role of ion migration. This study delves into the fundamental aspects of ion migration in halide perovskite nanocrystals. Porous electrodes for supercapacitor application were fabricated using CsPbBr3–xIx (x=0,1,2) nanocrystals prepared via the ligand‐assisted re‐precipitation (LARP) method. Three‐electrode electrochemical measurements and several other characterizations were conducted under dark conditions to evaluate device performance and elucidate the impact of mixed halides on device kinetics and stability. X‐ray photoelectron spectroscopy before and after the electrochemical measurement reveals intriguing findings. Notably, the analysis uncovered the phase segregation in the metal halide perovskite nanocrystals with particular emphasis on CsPbBr2I due to its distinctive mixed‐halide behavior. The specific capacitance increases with the increasing cycles. Interestingly, as the iodide content increases, there is no selective halide expulsion as the structure collapses rapidly.

Highly sensitive room-temperature ammonia sensor based on PbS quantum dots modified SnS2 nanosheets and theoretical investigation on its sensing mechanism by DFT calculation

Real-time accurate detection of hazardous gases is an urgent issue for industrial development and safeguarding public health. However, large-scale application of gas sensors in the network requires low-power consumption of sensing device for successful integration in smart platform. Although traditional ammonia (NH3) sensors based on semiconductor materials possess various advantages, it still remains the challenge in high operating temperature. Herein, PbS quantum dots (QDs) with higher adsorption energy were used to sensitize SnS2 nanosheets with electron transport capacity to achieve excellent NH3 sensing performance. PbS QDs with an approximately diameter of 10 nm were dispersed on SnS2 nanosheets with an average thickness of 14 nm. Impressively, the optimal sensor employing PbS QDs/SnS2 nanocomposites exhibited high sensor response of 8.5 to 100 ppm NH3, good response/recovery times of 9 s/720 s, as well as excellent selectivity, repeatability, and long-term stability at room temperature of 25 °C. The adsorption behavior and electronic structure of PbS QDs/SnS2 nanocomposites before and after NH3 adsorption were investigated based on density functional theory calculation. Moreover, the sensing mechanism of PbS QDs/SnS2 nanocomposites was also discussed. The designed PbS QDs/SnS2 nanocomposites hold considerable promise as a candidate in realizing superior NH3 sensing performance at room temperature.

Structures, simulated photoelectron spectroscopy, and electronic properties of CuASix(A = Sc, Cu, x ≤ 13) clusters: Relatively stable neutral pentagonal bipyramid structures of CuASi5

Structural design and optimization, simulated photoelectron spectroscopy, electronic properties and chemical bond analysis of CuASix(A = Sc, Cu, x ≤ 13) clusters were systematically studied using the PBE scheme to integrate with global search program of ABCluster. Firstly, neutral MS (the most stable structures) of CuASi5 of the basic 1 + 5 + 1 structures (1 metal + 5 silicons + 1 metal atoms) can be found as the basic units for assembling more lager clusters under the condition of neglecting distortions and minor changes. If the Cu atoms in Cu2Six(x ≤ 13) systems was replaced by one Sc atom, the geometries of MS will be reconstructed. Compared with the wheel geometries of Cu2Si12 and Cu2Si13, CuScSi12 and CuScSi13 clusters belong to near-wheel geometries with peripheral metal atoms. The neutral CuScSi5 and Cu2Si5 clusters possess relatively higher stability in all of cluster sizes. A combination of NPA analysis of CuASi5, sp of the Cu atom and spd of the Sc atom hybridizations were crucial to the chemical bonds of A–Si in the neutral CuASi5 clusters. In view of the higher SED value of the Cu2Si5 molecule, chemical bond analysis was carried out using MO, HLg and AdNDP analysis. 18 localized bonds and four delocalized bonds can play a positive role for the relative stabilities of neutral pentagonal bipyramid structures of Cu2Si5. Thus, the Cu2Si5 cluster with a lager HLg(1.80 eV) may be a good candidate for the basic unit of silicon-based semiconductor material assembly.