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1.
In this paper, we report a systematic investigation of the near band edge (NBE) excitonic states in GaN using low temperature photoluminescence (PL) and photoreflectance (PR) measurements. For this purpose, GaN films of different thicknesses have been grown on silicon nitride (SiN) treated c-plane sapphire substrates by atmospheric pressure metalorganic vapor phase epitaxy (MOVPE). Low temperature PR spectra exhibit well-defined spectral features related to the A, B and C free excitons denoted by FXA FXB and FXC, respectively. In contrast, PL spectra are essentially dominated by the A free and donor bound excitons. By combining PR spectra and Hall measurements a strong correlation between residual electron concentration and exciton linewidths is observed. From the temperature dependence of the excitonic linewidths, the exciton-acoustic phonon coupling constant is determined for FXA, FXB and FXC. We show that this coupling constant is strongly related to the exciton kinetic energy and to the strain level. 相似文献
2.
Hiroyasu Sato 《应用有机金属化学》1991,5(4):207-219
This is meant to be a brief overview of the developments of research activities in Japan on organometallic compounds related to their use in electronic and optoelectronic devices. The importance of organometallic compounds in the deposition of metal and semiconductor films for the fabrication of many electronic and opto-electronic devices cannot be exaggerated. Their scope has now extended to thin-film electronic ceramics and high-temperature oxide superconductors. A variety of organometallic compounds have been used as source materials in many types of processing procedures, such as metal–organic chemical vapor deposition (MOCVD), metalorganic vapor-phase epitaxy (MOVPE), metal–organic molecular-beam epitaxy (MOMBE), etc. Deposited materials include silicon, Group III–V and II–VI compound semiconductors, metals, superconducting oxides and other inorganic materials. Organometallic compounds are utilized as such in many electronic and optoelectronic devices; examples are conducting and semiconducting materials, photovoltaic, photochromic, electrochromic and nonlinear optical materials. This review consists of two parts: (I) research related to the fabrication of semiconductor, metal and inorganic materials; and (II) research related to the direct use of organometallic materials and basic fundamental research. 相似文献
3.
以一水合乙酸铜和苯胺为原料, 合成了铜掺杂纳米碳点(Cu-CDs). 通过优化实验参数, 确定了合成Cu-CDs的最佳反应时间、 反应温度和原料摩尔比分别为5 h, 210 ℃和1∶1. 与相同条件下的对照实验相比, Cu的掺杂使碳点(CDs)的荧光强度明显提高, 并实现了良好的多色发光性能. 在365 nm紫外光激发下, Cu-CDs可直接发射强烈的白光. 进一步与紫外发光二极管(LED)芯片结合, 得到白色发光器件, 色坐标为(0.337, 0.337), 非常接近纯白光的色坐标(0.33, 0.33). 这种制备Cu-CDs材料的方法及突出的白光发射性能, 拓宽了碳点在发光器件中的应用. 相似文献
4.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(17):4817-4821
Ta3N5 is a very promising photocatalyst for solar water splitting because of its wide spectrum solar energy utilization up to 600 nm and suitable energy band position straddling the water splitting redox reactions. However, its development has long been impeded by poor compatibility with electrolytes. Herein, we demonstrate a simple sputtering‐nitridation process to fabricate high‐performance Ta3N5 film photoanodes owing to successful synthesis of the vital TaOδ precursors. An effective GaN coating strategy is developed to remarkably stabilize Ta3N5 by forming a crystalline nitride‐on‐nitride structure with an improved nitride/electrolyte interface. A stable, high photocurrent density of 8 mA cm−2 was obtained with a CoPi/GaN/Ta3N5 photoanode at 1.2 VRHE under simulated sunlight, with O2 and H2 generated at a Faraday efficiency of unity over 12 h. Our vapor‐phase deposition method can be used to fabricate high‐performance (oxy)nitrides for practical photoelectrochemical applications. 相似文献
5.
Mohd Zaki Mohd Yusoff Zainuriah Hassan Chin Che Woei Haslan Abu Hassan 《化学物理学报(中文版)》2010,23(4):431-436
We investigated growth of GaN pn-junction layers grown on silicon(111) by plasma-assisted molecular beam epitaxy system and its application for photo-devices. Si and Mg were used as n- and p-dopants, respectively. The reflection high energy electron diffraction images indicated a good surface morphology of GaN pn-junction layer. The thickness of GaN pn-junctions layers was about 0.705 nm. The absence of cubic phase GaN showed that this layer possessed hexagonal structure. According to XRD symmetric rocking curve ω/2θ scans of (0002) plane at room temperature, the full width at half-maximun of GaN pn-junction sample was calculated as 0.34o, indicating a high quality layer of GaN pn-junction. Surprisingly, there was no quenching of the A1(LO) peak, with the presence of Si- and Mg-dopants in sample. The pn-junctions sample has a good optical quality which was measured by thephotoluminescence system. For photo-devices applications, Ni and Al were used as front and back contacts, respectively. The current-voltage characteristics of the devices showed the typical rectifying behavior of heterojunction. The photo-current measurement was performed using a visible-lamp under forward and reverse biases. From the temperature-dependent measurements, the current at low bias exhibited much stronger temperature dependence and weaker field dependence. The effect of thermal annealing on front contact Ni was also carried out. The front contact Ni was annealed at 400 and 600 oC for 10 min in the nitrogen ambient. The results showed that 600 oC treated sample had a higher gain at 1.00 V/e than 400 oC treated and untreated samples. 相似文献
6.
Moving Graphitic Carbon Nitride from Electrocatalysis and Photocatalysis to a Potential Electrode Material for Photoelectric Devices
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Carbon nitride (g‐CN) has attracted significant interest in the last years as a robust, low‐cost alternative to metal‐based materials in different fields due to its low price, environmentally benign character, simple synthesis and tunable properties. In particular, g‐CN demonstrates promising activity in energy‐related applications such as photo and heterogeneous catalysis, batteries and electrolysis. However, while g‐CN is already well‐established as a photocatalyst, its utilization in (opto)electronic devices is still at an early stage. This Focus Review concentrates on the utilization of g‐CN in solar and photoelectrochemical cells, electrolyzers and light emitting diode alongside the recap of new synthetic approaches. This review is expected to provide useful insights into the design and fabrication of g‐CN based photoelectronic devices as well as g‐CN working principles, including the main challenges toward its integration in optoelectronic devices. 相似文献
7.
以邻苯二胺、 2,5-二氨基苯磺酸和三氯化铝为原料, 通过无溶剂法大量制备了高效的红色荧光碳点 (R-CDs). 制得的碳点尺寸大约为2.4 nm, 含有13%的氮元素, 主要由高度石墨化的碳核及覆盖在其表面的大量官能团构成. 在不同的波长光激发下, 碳点在乙醇溶液中表现出不依赖于激发的红光发射, 其荧光峰位于 704 nm, 最大量子产率达到22%. 由于R-CDs具有优异的光学性质, 利用其构筑了紫外光激发的碳基白色发光二极管, 其色坐标为(0.33, 0.33), 非常接近自然光. 该研究为高效红色荧光碳点的大量制备提供了一种新路径, 同时拓宽了其在白光器件中的应用. 相似文献
8.
The structure and reactivity of discrete iron nitride complexes is described. Six-coordinate, four-fold symmetric nitrides are thermally unstable, and have been characterized at cryogenic temperatures by an arsenal of spectroscopic methods. By contrast, four-coordinate, three-fold symmetric iron nitrides can be prepared at room temperature. A range of diamagnetic iron(IV) nitrides have been reported and in some cases, isolated. Among these are the isolable, yet reactive, tris(carbene)borate iron(IV) nitrides. These complexes can effect two-electron nitrogen atom transfer to a range of substrates, in some cases with complete atom transfer occuring through Fe-N bond cleavage. These nitrides are also active in single electron pathways, including the synthesis of ammonia by a mechanism involving hydrogen atom transfer to the nitride ligand. One-electron oxidation of a tris(carbene)borate iron(IV) nitride leads to an isolable iron(V) complex that is unusually reactive for a metal nitride. 相似文献
9.
Tao Yu-Tai 《合成化学》2004,12(Z1)
An efficient and stable white organic light emitting diode (WOLED) is highly desirable in potential applications such as lighting, background light source, and full color display.A series of highly fluorescent dyes based on a dipyrazolopyridine skeleton,1,7-diphenyl-l,7-dihydrodipyrazolo[3,4-b,4′,3′-e]pyridine, were synthesized and evaluated as emitting as well as charge-transporting material in the fabrication of electroluminescent devices.Several of the blue derivatives are found to be useful as the source of blue emission in fabricating bright white-emitting devices. The choice of dopants, cathode materials, electron-transporting materials as well as the device configurations greatly affect the emission profile, efficiencies, as well as the device lifetime. The latest progress in achieving a more efficient, color stable, durable white light device will be discussed. 相似文献
10.
In vapor-liquid-solid (VLS) growth, it is generally believed that nanowires would grow as long as the right catalysts and substrate are supplied as well as the growth temperature is adequate. We show here, however, that oxygen partial pressure plays a key role in determining the quality of the aligned ZnO nanowires. We present a "phase diagram" between the oxygen partial pressure and the growth chamber pressure for synthesizing high quality aligned ZnO nanowires on GaN substrate. This result provides a road map for large-scale, controlled synthesis of ZnO nanowires on nitride semiconductor substrates with the potential to meet the needs of practical applications. The chemical process involved in the growth process is also systematically elaborated based on experimental data received under different conditions. 相似文献
11.
Liang Liao Ali Cirpan Liming Ding Frank E. Karasz Yi Pang 《Journal of polymer science. Part A, Polymer chemistry》2006,44(7):2307-2315
New poly(phenylene vinylene) derivatives with a 5‐diphenylamino‐1,3‐phenylene linkage (including polymers 2 , 3 , and 5 ) have been synthesized to improve the charge‐injection properties. These polymers are highly photoluminescent with fluorescent quantum yields as high as 76% in tetrahydrofuran solutions. With effective π‐conjugation interruption at adjacent m‐phenylene units, chromophores of different conjugation lengths can be incorporated into the polymer chain in a controllable manner. In polymer 2 , the structural regularity leads to an isolated, well‐defined emitting chromophore. Isomeric polymer 3 of a random chain sequence, however, allows the effective emitting chromophores to be joined in sequence by sharing a common m‐phenylene linkage (as shown in a molecular fragment). Double‐layer light‐emitting‐diode devices using 2 , 3 , and 5 as emitting layers have turn‐on voltages of about 3.5 V and produce blue‐green emissions with peaks at 493, 492, and 482 nm and external quantum efficiencies up to 1.42, 0.98, and 1.53%, respectively. In comparison with a light‐emitting diode using 2 , a device using 3 shows improved charge injection and displays increased brightness by a factor of ~3 to 1400 cd/m2 at an 8‐V bias. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2307–2315, 2006 相似文献
12.
We reported the growth of N-polar InN films on N-polar GaN/sapphire substrates by pulsed metal-organic vapor phase epitaxy. The crystalline quality, surface morphology, optical and electrical properties of N-polar InN films were investigated in details by varying the breaking time and trimethylindium(TMIn) duration of pulse cycle. It has been found that when the breaking time and the TMIn duration in each cycle remain at 30 and 60 s, respectively, the N-polar InN film obtained exhibits a better crystalline quality and greater optical properties. Meanwhile, the surface morphology and electrical properties of the N-polar InN films also greatly depend on the given growth conditions. 相似文献
13.
14.
《Comptes Rendus de l''Academie des Sciences Series IIB Mechanics Physics Astronomy》1999,2(9-10):483-485
GaN, a large band-gap semiconductor (3.49 eV), is a very promising material concerning the optoelectronic and microelectronic areas, mainly due to the value of the band gap and also to its high chemical and thermal stability. Most of the work concerning this nitride implies the formation of thin films by various techniques of epitaxy. The solvothermal synthesis is a new route to obtain GaN. This process is conducted in a nitriding solvent in the supercritical state (T > Tc and P > Pc) or close to it. In such conditions, the diffusion of the chemical species is enhanced. Microcrystallites of GaN of good chemical purity have been obtained by this process. The obtained microcrystallites have been characterised by several techniques: X ray diffraction and scanning electron microscopy. 相似文献
15.
Martin Lerch Jürgen Janek Klaus D. Becker Stefan Berendts Hans Boysen Thomas Bredow Richard Dronskowski Stefan G. Ebbinghaus Martin Kilo Marck W. Lumey Manfred Martin Christoph Reimann Eberhard Schweda Ilia Valov Hans D. Wiemhöfer 《Progress in Solid State Chemistry》2009,37(2-3):81-131
The possibility of fast nitrogen ion conduction in solids is reviewed. Promising electrolytes based on three different base compounds are in the focus of this contribution: Zirconium oxide nitrides, tantalum oxide nitrides and mayenite-based materials. All aspects ranging from preparation methods, crystal structures (ideal and defect structure, also at elevated temperatures), transport properties (ionic and electronic conductivity, transference numbers, diffusion) and correlations between structure and physical properties are presented and discussed, in part also in relation to theoretical calculations. Fluorite-type quaternary oxide nitrides of zirconium are proven to be the first known materials with high nitrogen ion mobility. They can be described as fast mixed oxygen/nitrogen conductors but are limited due to the low maximum nitrogen/oxygen ratio achievable. Corresponding phases based on stabilized tantalum oxide nitrides have a superior N/O ratio but show poor thermal stability. For the development of a pure nitrogen ion conductor a different approach has also been investigated: Some cage compounds, in particular mayenite, allow the substitution of oxygen anions not tightly bound in the framework by nitrogen ions. Some of the obtained N-containing phases exhibit an outstanding electrical conductivity at low temperatures. Possible devices and applications such as a new type of a nitrogen sensor and an ammonia-producing fuel cell are introduced and discussed. 相似文献
16.
Rafaja D Wüstefeld C Motylenko M Schimpf C Barsukova T Schwarz MR Kroke E 《Chemical Society reviews》2012,41(15):5081-5101
Mechanical properties of nanocomposites usually surpass the mechanical properties of their micro-structured and single-crystalline counterparts. This is mainly due to an extremely high density of internal interfaces in nanocomposites like grain, crystallite and phase boundaries. When compared to diamond, carbides and borides, nitrides are of interest because of their high temperature oxidation resistance and compatibility with iron containing alloys. This tutorial review classifies the contributions of various internal interfaces to the hardness of the nanocomposites, and appreciates the outstanding role of partially coherent phase boundaries in the hardness enhancement. With selected examples of transition metal nitrides containing aluminium and silicon as well as of boron nitrides, it is explained how the nanocomposites with partially coherent phase boundaries and thus with enhanced hardness can be synthesised. As the possible ways of the formation of coherent phase boundaries, the local epitaxial growth of phases with limited mutual solubility, the production of supersaturated solid solutions followed by the segregation of elements during the spinodal decomposition and the incomplete phase transformation are discussed. The most important techniques, used for synthesis of nitride nanocomposites, like CVD, PVD, precursor-based methods, mechanical alloying and high-pressure-high-temperature synthesis are briefly reviewed. Besides, a short overview on hardness definitions and hardness measurements is included. 相似文献
17.
Yu‐Ling Wang Shuai Chang Xiao‐Mei Chen Yan‐Dong Ren Li‐Fu Shi Yong‐Hao Liu Hai‐Zheng Zhong 《中国化学》2019,37(6):616-629
Metal halide perovskites are emerging as new generation optoelectronic materials due to their high carrier mobility, long carrier diffusion length and large light absorption coefficient, which have broad applications in solar cell, light‐emitting diode, laser, photodetector and transistors. Perovskite single crystal is an ideal platform for discerning the intrinsic properties of these materials. In some cases, perovskite single crystals are better candidates to gain high performance optoelectronics. However, the growth of perovskite single crystals is time and cost consuming, which has an obvious disadvantage for device exploration. Therefore, fast growth technique is highly desirable in not only promoting the use of perovskites in commercial applications but also facilitating deep physical investigation of the materials. In this review, we summarize thoroughly the development of fast growth of the halide perovskites single crystal. Specifically, we highlight the progress of rapid growth techniques with emphasis on the optimization control. 相似文献
18.
Jeong-Hwan Park Xu Yang Jun-Yeob Lee Mun-Do Park Si-Young Bae Markus Pristovsek Hiroshi Amano Dong-Seon Lee 《Chemical science》2021,12(22):7713
A challenging approach, but one providing a key solution to material growth, remote epitaxy (RE)—a novel concept related to van der Waals epitaxy (vdWE)—requires the stability of a two-dimensional (2-D) material. However, when graphene, a representative 2-D material, is present on substrates that have a nitrogen atom, graphene loss occurs. Although this phenomenon has remained a hurdle for over a decade, restricting the advantages of applying graphene in the growth of III-nitride materials, few previous studies have been conducted. Here, we report the stability of graphene on substrates containing oxygen or nitrogen atoms. Graphene has been observed on highly decomposed Al2O3; however, graphene loss occurred on decomposed AlN at temperatures over 1300 °C. To overcome graphene loss, we investigated 2-D hexagonal boron nitride (h-BN) as an alternative. Unlike graphene on AlN, it was confirmed that h-BN on AlN was intact after the same high-temperature process. Moreover, the overgrown AlN layers on both h-BN/AlN and h-BN/Al2O3 could be successfully exfoliated, which indicates that 2-D h-BN survived after AlN growth and underlines its availability for the vdWE/RE of III-nitrides with further mechanical transfer. By enhancing the stability of the 2-D material on the substrate, our study provides insights into the realization of a novel epitaxy concept.A challenging approach, but one providing a key solution to material growth, remote epitaxy (RE)—a novel concept related to van der Waals epitaxy (vdWE)—requires the stability of a two-dimensional (2-D) material. 相似文献
19.
Ha B Seo SH Cho JH Yoon CS Yoo J Yi GC Park CY Lee CJ 《The journal of physical chemistry. B》2005,109(22):11095-11099
Thin high-quality gallium nitride (GaN) nanowires were synthesized by a catalytic chemical vapor deposition method. The synthesized GaN nanowires with hexagonal single-crystalline structure had thin diameters of 10-50 nm and lengths of tens of micrometers. The thin GaN nanowires revealed UV bands at 3.481 and 3.285 eV in low-temperature PL measurements due to the recombination of donor-bound excitons and donor-acceptor pairs, respectively. The blue shifts of UV bands in the low-temperature PL measurement were observed, indicating quantum confinement effects in the thin GaN nanowires which have smaller diameters than the exciton Bohr radius, 11 nm. For field emission properties of GaN nanowires, the turn-on field of GaN nanowires was 8.5 V/microm and the current density was about 0.2 mA/cm(2) at 17.5 V/microm, which is sufficient for the applications of field emission displays and vacuum microelectronic devices. Moreover, the GaN nanowires indicated stronger emission stability compared with carbon nanotubes. 相似文献
20.
Tsuyoshi Tsujioka 《Chemical record (New York, N.Y.)》2016,16(1):231-248
Selective metal‐vapor deposition signifies that metal‐vapor atoms are deposited on a hard organic surface, but not on a soft (low glass transition temperature, low Tg) surface. In this paper, we introduce the origin, extension, and applications of selective metal‐vapor deposition. An amorphous photochromic diarylethene film shows light‐controlled selective metal‐vapor deposition, which is caused by a large Tg change based on photoisomerization, but various organic surfaces, including organic crystal and polymers, can be utilized for achieving selective metal‐vapor deposition. Various applications of selective metal‐vapor deposition, including cathode patterning of organic light‐emitting devices, micro‐thin‐film fuses, multifunctional diffraction gratings, in‐plane electrical bistability for memory devices, and metal‐vapor integration, have been demonstrated. 相似文献