Epitaxial ZnO films grown by RF-assisted low-temperature CVD method

A low-temperature modification of the Chemical vapor deposition (CVD) growth with the RF-discharge plasma generated in CVD reactor during the growth process has been reported. This method allows us to significantly increase the effective pressure of atomic oxygen during the deposition, and to shift the stoichiometry of the growing film to oxygen excess. With RF activation we could lower the substrate temperature by more than 200°C, down to 420°C. The obtained zinc oxide/α-sapphire films feature high crystallinity, perfect surface morphology and good electrical and optical properties at the expense of both the decrease in the width of the transition layer and amount of the uncontrolled impurities.     

多晶硅、单晶硅同步外延研究

介绍了多晶硅、单晶硅的同步外延.采用两步外延工艺,研究了硅烷流量、外延时间以及外延温度对外延质量参数α的影响.硅烷流量大、初始诱生时间短,则单晶硅条宽,多晶硅横向蔓延弱,但外延层质量可能较差.较优的条件是:硅烷诱生生长流量为13.1～17.5sccm,正常生长流量为7.0～7.88sccm,初始诱生时间为30～50s.温度影响较复杂,当温度低于980℃时,单晶硅条宽随温度增加而增加,在980℃附近达到最大,随后随温度增加单晶条宽降低.     

化学气相沉积4H-SiC同质外延膜的生长及其特征

采用常压化学气相沉积（APCVD）方法在偏向〈1120〉晶向8. 的p型4H-SiC (0001) Si-面衬底上进行同质外延生长. 霍尔测试的结果表明，非有意掺杂的外延膜层导电性为n型. XRD测试显示各个样品只在位于2θ=355. 附近出现一个谱峰，表明外延膜是SiC单晶. 在低温PL谱中，对于在较低温度下外延生长的4H-SiC样品，在1.8～2.4eV范围内出现很宽的谱峰. 而在该样品的Raman谱中，也观察到了典型的3C-SiC的特征峰，表明该样品含有立方相SiC的混晶，这与PL谱获得的结果相吻合.     

Processing and properties of CVD diamond for thermal management

One of the many remarkable properties of diamond is its thermal conductivity, about five times that of copper and the highest of all known materials. The high thermal conductivity in combination with the relative ease of diamond film growth by chemical vapor deposition process makes the material suitable for many applications such as thermal management in high power electronic circuits. For thermal managements applications, various processing steps are needed for the diamond films, such as the metallization for reliable solder bonding, metallurgical processes for planarizing of the faceted growth surface and removal of fine-grained diamond regions with poor thermal conductivity. This paper will review the properties and processing of diamond films for thermal management applications.     

Recent developments in CVD growth and applications of 2D transition metal dichalcogenides

Two-dimensional (2D) transition metal dichalcogenides (TMDs) with fascinating electronic energy band structures, rich valley physical properties and strong spin–orbit coupling have attracted tremendous interest, and show great potential in electronic, optoelectronic, spintronic and valleytronic fields. Stacking 2D TMDs have provided unprecedented opportunities for constructing artificial functional structures. Due to the low cost, high yield and industrial compatibility, chemical vapor deposition (CVD) is regarded as one of the most promising growth strategies to obtain high-quality and large-area 2D TMDs and heterostructures. Here, state-of-the-art strategies for preparing TMDs details of growth control and related heterostructures construction via CVD method are reviewed and discussed, including wafer-scale synthesis, phase transition, doping, alloy and stacking engineering. Meanwhile, recent progress on the application of multi-functional devices is highlighted based on 2D TMDs. Finally, challenges and prospects are proposed for the practical device applications of 2D TMDs.     

Interactions of DNA with graphene and sensing applications of graphene field-effect transistor devices: A review

Graphene field-effect transistors (GFET) have emerged as powerful detection platforms enabled by the advent of chemical vapor deposition (CVD) production of the unique atomically thin 2D material on a large scale. DNA aptamers, short target-specific oligonucleotides, are excellent sensor moieties for GFETs due to their strong affinity to graphene, relatively short chain-length, selectivity, and a high degree of analyte variability. However, the interaction between DNA and graphene is not fully understood, leading to questions about the structure of surface-bound DNA, including the morphology of DNA nanostructures and the nature of the electronic response seen from analyte binding. This review critically evaluates recent insights into the nature of the DNA graphene interaction and its affect on sensor viability for DNA, small molecules, and proteins with respect to previously established sensing methods. We first discuss the sorption of DNA to graphene to introduce the interactions and forces acting in DNA based GFET devices and how these forces can potentially affect the performance of increasingly popular DNA aptamers and even future DNA nanostructures as sensor substrates. Next, we discuss the novel use of GFETs to detect DNA and the underlying electronic phenomena that are typically used as benchmarks for characterizing the analyte response of these devices. Finally, we address the use of DNA aptamers to increase the selectivity of GFET sensors for small molecules and proteins and compare them with other, state of the art, detection methods.     

Glass fabrics self-cracking catalytic growth of boron nitride nanotubes

Glass fabrics were used to fabricate boron nitride nanotubes (BNNTs) with a broad diameter range through a combined chemical vapor deposition and self-propagation high-temperature synthesis (CVD-SHS) method at different holding times (0min, 30min, 90min, 180min and 360min). SEM characterization has been employed to investigate the macro and micro structure/morphology changes of the glass fabrics and BNNTs in detail. SEM image analysis has provided direct experimental evidences for the rationality of the optimized self-cracking catalyst VLS growth mechanism, including the transformation situations of the glass fabrics and the BNNTs growth processes respectively. This paper was the further research and compensation for the theory and experiment deficiencies in the new preparation method of BNNTs reported in our previous work. In addition, it is likely that the distinctive self-cracking catalyst VLS growth mechanism could provide a new idea to preparation of other inorganic functional nano-materials using similar one-dimensional raw materials as growth templates and catalysts.     

液态源可控蒸发输送系统

在太阳能电池、微电子等半导体工艺制程中,液态源以生产效率高、成膜特性好、气压小不易泄漏等优点,广泛应用于扩散、氧化、化学气相沉积等工艺。如:在太阳能电池PN结制程中,掺杂用的液态磷源、液态硼源,以及在湿氧氧化工艺中使用的蒸馏水;在光电子、微电子行业中,化学气相淀积设备(CVD)使用的HMDSO、TEOS、SiHCl3等。实验数据显示,这些液态源的输送对各种掺杂、氧化、淀积工艺的质量具有很大影响。对液态源输送的技术现状进行阐述,分析了现有技术的特性和缺点,并结合未来工艺对装备要求的趋势,在此基础上提出了一种液态源可控蒸发输送系统。     

Growth behavior and improved water–vapor-permeation-barrier properties of 10-nm-thick single Al2O3 layer grown via cyclic chemical vapor deposition on organic light-emitting diodes

We have investigated the growth behavior and water vapor permeation barrier properties of cyclic chemical vapor deposition (C-CVD)-grown 10-nm-thick single layer of Al₂O₃. Al₂O₃ layers grown by C-CVD showed a high density of 3.298 g/cm³ and were amorphous without grain boundaries. A deposition rate of 0.46 nm/cycle was obtained. The C-CVD system was self-limiting, as in the case of atomic layer deposition, which enables precise control of the thickness of the Al₂O₃ layer. A water vapor transmission rate of 1.51 × 10⁻⁵ (g/m²)/day was obtained from a Ca degradation test performed at 85 °C and 85% relative humidity. Moreover, the performance of organic light-emitting diodes, passivated by a C-CVD-grown 10-nm-thick Al₂O₃ single layer, was not affected after 24,000 h of turn-on time; this is strong evidence that C-CVD-grown Al₂O₃ layers effectively prevent water vapor from diffusing into the active organic layer.     

Wide‐Area Strain Sensors based upon Graphene‐Polymer Composite Coatings Probed by Raman Spectroscopy

Functional graphene optical sensors are now viable due to the recent developments in hand‐held Raman spectroscopy and the chemical vapor deposition (CVD) of graphene films. Herein, the strain in graphene/poly (methyl methacrylate) sensor coatings is followed using Raman band shifts. The performance of an “ideal” mechanically‐exfoliated single crystal graphene flake is compared to a scalable CVD graphene film. The dry‐transferred mechanically exfoliated sample has no residual stresses, whereas the CVD sample is in compression following the solvent evaporation during its transfer. The behavior of the sensors under cyclic deformation shows an initial breakdown of the graphene‐polymer interface with the interface then stabilizing after several cycles. The Raman 2D band shift rates per unit strain of the exfoliated graphene are ≈35% higher than CVD graphene making the former more strain sensitive. However, for practical wide‐area applications, CVD graphene coatings are still viable candidates as a Raman system can be used to read the strain in any 5 μm diameter spot in the coating to an absolute accuracy of ≈0.01% strain and resolution of ≈27 microstrains (μs), which compares favorably to commercial photoelastic systems.