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In recent years, organic-inorganic hybrid lead halide perovskite materials have attracted much attention in the world because of their excellent photoelectric properties, and have been successfully applied in many fields such as solar photovoltaic, photoelectric detection, electroluminescence and so on. At present, most of the device research focuses on perovskite polycrystalline materials, but perovskite single crystal materials have excellent properties such as lower defect state density, higher carrier mobility, longer carrier recombination lifetime, wider light absorption range and higher stability, which can effectively reduce the scattering loss during carrier transport and non-radiative recombination at the grain boundary, and inhibit the hysteresis effect caused by ion migration. Using perovskite single crystal thin film as the active layer of the device is expected to produce more efficient and stable perovskite photoelectric devices. At present, many preparation methods of perovskite single crystal films have been reported, mainly including solution-processed space-confined method, chemical vapor deposition method, top-down processing method, etc. Among them, solution-processed space-confined method is the most widely developed and applied. This paper focuses on the preparation of high-quality perovskite single crystal thin films by solution-processed space-confined method, and the research progress of perovskite single crystal thin films in photodetectors, solar cells, field effect transistors, light-emitting diodes and other related devices, and prospects the future development trend of perovskite single crystal thin films and photoelectric devices. [ABSTRACT FROM AUTHOR]

BaTiO3 has become the key materials for the preparation of high-performance electro-optical modulators due to its high electro-optical coefficient, excellent piezoelectric properties and nonlinear optical properties. The quality, growth orientation and electro-optic coefficient of the film are determined by the preparation method, experimental condition and the selection of substrate, and further affecting the propagation loss, half-wave voltage and extinction ratio of the electro-optical modulator. Based on the working principle of electro-optical modulator, the factors affecting the orientation and quality of film forming were discussed by focusing on the preparation methods, experimental conditions and film substrates of BaTiO3 thin film in this paper. The advantages and disadvantages of each process of BaTiO3 thin film preparation were analyzed, the structure and performance of waveguide were discussed. Finally, the direction of optimizing BaTiO3 thin film fabrication and waveguide fabrication process in the future were summarized in this paper. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Synthetic Crystals is the property of Journal of Synthetic Crystals Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper mainly studies the preparation process of N-type high-efficient crystalline silicon tunnel oxide passivated contact (TOPCon) cells by low pressure chemical vapor deposition (LPCVD) method. The influencing factors of the preparation of tunnel oxide layer and polycrystalline silicon layer by LPCVD were studied and analyzed. The effects of different oxide layer thickness, polysilicon thickness and polysilicon doping amount on the efficiency were studied. The results show that: the thickness of tunneling oxide layer of 1.55 nm shows the best passivation effect; the Voc reaches the highest value when the thickness of polysilicon layer is 120 nm; the Eff reaches the highest when the thickness of polysilicon layer is 90 nm. The field passivation effect of polysilicon layer increases with the increase of P doping concentration. Higher Voc can be obtained when the P doping concentration is 3.0 x 1015 cm-2. [ABSTRACT FROM AUTHOR]

Two-dimensional transition metal dichalcogenides (TMDs) are a new type of two-dimensional materials after graphene. Due to their unique physical and chemical properties, much attention has been attracted in semiconductors, optoelectronic materials, energy storage, and catalytic hydrogen production. Chemical vapor deposition (CVD) is currently one of the processes suitable for realizing large-scale preparation of two-dimensional materials. Due to the highly controllable parameters of CVD process, it has great advantages in the preparation of two-dimension materials. In this paper, the recent research progress on preparation of TMDs by CVD is reviewed, and the influence of various factors on the growth and final morphology of the products in CVD preparation process, including precursors, temperature, substrate, auxiliaries, pressure and carrier gas are discussed. Some improved CVD processes are listed and their characteristics are also summarized. Finally, challenges and prospects for the development of TMDs prepared by CVD are discussed. [ABSTRACT FROM AUTHOR]

In this paper, the effect of introducting different concentration CO2 into reaction gas on the internal stress of single crystal diamond grown by microwave plasma chemical vapor deposition (MPCVD) homogeneous epitaxy was studied, and its mechanism was analyzed. Results show that with the increase of CO2 concentration, the internal stress of single crystal diamond decreases gradually. This is because the added CO2 provides oxygen containing groups, which can effectively etch the non-diamond carbon in the diamond growth process, and reduce the content of impurities in the diamond, so as to avoid lattice distortion and reduce growth defects. This ultimately shows the reduction of the internal stress of single crystal diamond, which is in the form of compressive stress. Besides, the addition of CO2 in reaction gas can reduce the growth rate and deposition temperature of single crystal diamond, and single crystal diamond with less impurities and high crystallinity can be obtained at a suitable carbon hydrogen oxygen atomic ratio (5:112:4). [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) is an ideal electronic material for high temperature, high frequency, and high power electronic devices. In last 20 years, with the continous development of epitaxial equipment and process, the film growth rate and quality of SiC have been significantly improved, which leads more and more applications in various industrial fields such as new energy vehicles, photovoltaic industry, high-voltage transmission industry and intelligent power stations. Different from the silicon semiconductor industry, silicon carbide devices must be processed on the epitaxial film. Therefore, silicon carbide epitaxial equipment plays an critical connecting role in the whole industrial chain, and it is also the most complex and difficult to develop equipment in the whole industrial chain. In this paper, the SiC pitaxial mechanism is briefly described. The progress of several important aspects of the SiC-chemical vapor deposition (CVD) equipment, such as reactor chamber, heating system and rotation system etc. are reviewed. The outlook for the future research key areas and direction of SiC is also given. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Synthetic Crystals is the property of Journal of Synthetic Crystals Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The excellent physical properties of diamond make it one of the most promising semiconductor materials for the next generation. At present, heteroepitaxy based on microwave plasma chemical vapor deposition may be the best method for preparing large-scale single crystal diamond in the future. In the past three decades, some progress has been made in the heteroepitaxial growth of single crystal diamond on iridium-based composite substrates, especially in recent years, the growth of large-scale single crystal diamond of more than 2 inch has been realized. This paper summarizes the various substrates used for diamond heteroepitaxy, briefly introduces bias-enhanced nucleation on heterogeneous substrates, and details the most successful iridium/ oxide, iridium/ oxide layer/ silicon composite substrates. In the end, the problems existing in diamond heterogeneous substrates and heteroepitaxy are summarized, and some possible solutions are given. [ABSTRACT FROM AUTHOR]

A novel coupled barrier heterojunction structure ( i. e. Al 0. 26 Ga0. 74 N/ GaN/ Al 0. 20 Ga0. 80 N/ GaN) was proposed and prepared in this paper to improve transconductance linearity of GaN high electron mobility transistor. A double two-dimensional electron gas (2DEG) channel in the coupled barrier heterojunction structure is demonstrated by theoretically calculation and capacitance-voltage (C-V) measurement. 2DEG mobility of 1 510 cm 2·V - 1·s - 1 and sheet density of 9. 7 × 10 12 cm - 2 are obtained. Benefiting from the double channels, the transconductance profile of the device with coupled heterojunction barrier structure shows two peaks, and the voltage swing is 3. 0 V, which is 1. 5 times larger than that of normal structure. First-order and second-order derivative characteristics of transconductance indicate that the device of the coupled barrier structure has higher harmonic suppression capability. This study demonstrates a superiority of coupled barrier heterojunction in the area of high linearity application. [ABSTRACT FROM AUTHOR]

Due to its excellent physical properties, diamond is regarded as a next-generation semiconductor material. However, its extremely high hardness, brittleness, and corrosion resistance cause the diamond difficult to process, especially for large)size chemical vapor deposition (CVD) single crystal diamonds (SCD). Currently, researchers have not explored an efficient and low-cost method for ultra-precision processing diamond wafers. Based on the rotary infeed surface grinding, integrated processing technology of grinding and polishing by the concentric double grinding wheel was proposed in this paper. In one clamping, the SCD surface is flattened by the inner ring ceramic grinding wheel that the abrasive is diamond, and then the surface after grinding is polished by sol-gel ( SG) polishing wheel that the abrasives are diamond mixed with CuO. In the processing of grinding and polishing integration, the surface roughness of SCD can be reduced from about 46 nm to less than 0. 3 nm in a short time. In the grinding, the ceramic grinding wheel with diamond abrasive scratches the SCD surface at high speed. The strong mechanical action causes the large material removal, obtains nano-level smooth surface of SCD, and causes the surface amorphization. In the SG polishing, the diamond abrasive scratches the SCD surface at high speed to form a high)temperature and high-pressure environment, which further induces the oxidation-reduction reaction between the CuO powder and the amorphous carbon for realizing reactive polishing. The integrated processing technology of grinding and polishing provides a reference for the industrial production of SCD wafers and polycrystalline diamond (PCD) wafers in the future. [ABSTRACT FROM AUTHOR]

Diamond as an ultra-wide band gap semiconductor material shows excellent properties in thermal conductivity, carrier mobility and breakdown field strength, and has broad application prospects in the field of power electronics. The realization of p-type and n-type conduction is essential to fabricate diamond electronic devices. Between them, the development of p-type diamond is relatively mature, and boron is the mainstream doping element. However, the hole mobility decreases rapidly at a high doping concentration. The main doping element of n-type diamond is phosphorus. At present, there are still challenges such as deep impurity level, large ionization energy, and defects in diamond crystals after doping, resulting in low carrier concentration and mobility, and the resistivity is difficult to meet the requirements of devices. Therefore, the realization of high quality p-type and n-type diamond has become the focus of researchers. This paper mainly introduces the unique physical properties of single crystal diamond, outlines the basic principles and key parameters of the chemical vapor deposition method and ion implantation method of doping, then reviews the research progress on the p-type and n-type doping of single crystal diamond films by the two methods, systematically summarizes the facing problems and the prospects of future development. [ABSTRACT FROM AUTHOR]

Owing to their small volume, strong radiation resistance and fast time response, diamond detectors show the obvious advantage of application in nuclear radiation area. At early stage, diamond nuclear radiation detectors were made of natural diamond materials. With the development of chemical vapor deposition ( CVD ) diamond synthetic technology, the development and application of diamond radiation detector has been greatly promoted. In this paper, starting with the CVD synthetic diamond material, the impurities and defects that restrict the performance of diamond detectors, the synthetic process of CVD diamond, the characterization method of impurities and defects in detector grade diamond are analyzed systematically. Based on the performance indicators such as the product of carrier mobility and life, the charge collection efficiency of detector, etc., the effects of impurities and defects in CVD diamond on the performance of the detector are summarized. The application status of diamond nuclear radiation detectors abroad is introduced and the development prospect of domestic diamond nuclear radiation detectors is also viewed. [ABSTRACT FROM AUTHOR]

MEMS, deep space and deep sea exploration tasks put forward higher requirements for long-term and portable power supply. Due to its high energy density and stable power output, isotopic battery can continuously provide energy for Lunar Rover and seabed detector in extreme environments such as high and low temperature and no sunlight. As the main type of isotope battery, radio-voltaic effect isotope battery has been widely studied because of its high theoretical energy conversion efficiency and easy miniaturization, and it has been successfully applied to cardiac pacemaker. The isotope battery made of energy converters using semiconductor with wide band gap can obtain higher energy conversion efficiency. The 5. 5 eV band gap and radiation resistance of single crystal diamond make it the best choice for making energy converters for radio-voltaic effect isotope batteries. With the development of chemical vapor deposition technology, the epitaxial technology of diamond crystal has made rapid progress, which has laid a material foundation for the development of diamond semiconductor devices. The characteristics of common semiconductor materials for energy converters and radiation source materials for isotopic battery are compared in this paper, the basic principle of radio-voltaic effect is introduced, then the key parameters of radio-voltaic effect isotopic battery is analyzed, and the literatures on the research of diamond radio-voltaic effect isotopic battery are summarized. The development status and existing problems of diamond isotope battery are pointed out. By analyzing the current performance and application of hetero pn junction composed of diamond and other n-type semiconductor materials, the structural design of high-performance isotope battery based on diamond hetero pn junction is given, summarized and prospected. [ABSTRACT FROM AUTHOR]

Graphene grown by chemical vapor deposition has excellent mechanical, thermal and electrical properties, and has become the preferred material for a new generation of nanodevices. Theoretical research on the electronic properties of graphene will prompt the development and application of nanodevices. Based on the combination of density functional theory and non-equilibrium Green's function, the electronic structure characteristics of graphene and graphene/boron nitride with AA vertical stack structures were studied systematically in this paper. The results show that the band gap is zero at the high symmetry K point. In the range of 50 K to 400 K, the mobility of graphene decreases significantly with increasing temperature due to the electron-phonon interaction on Fermi surface. In addition, the characteristic analysis of energy band structures, density of states and electron density of graphene/boron nitride with different interlamellar space indicates that with the increase of layer spacing, the energy band gap decreases, and the energy difference between the conduction band and the valence band decreases. And increasing the number of atoms, the regularity of the change of the band gap opening between supercell and protocell structure of graphene / boron nitride is consistent, this can serve an guideline for the structural design of graphene-based devices. [ABSTRACT FROM AUTHOR]