Low-Temperature Pulsed-PECVD ZnO Thin-Film Transistors

We report high-quality ZnO thin films deposited at low temperature (200°C) by pulsed plasma-enhanced chemical vapor deposition (pulsed PECVD). Process byproducts are purged by weak oxidants N₂O or CO₂ to minimize parasitic CVD deposition, resulting in high-refractive-index thin films. Pulsed-PECVD-deposited ZnO thin-film transistors were fabricated on plasma-enhanced atomic layer deposition (PEALD) Al₂O₃ dielectric and have a field-effect mobility of 15 cm²/V s, subthreshold slope of 370 mV/dec, threshold voltage of 6.6 V, and current on/off ratio of 10⁸. Thin-film transistors (TFTs) on thermal SiO₂ dielectric have a field-effect mobility of 7.5 cm²/V s and threshold voltage of 14 V. For these devices, performance may be limited by the interface between the ZnO and the dielectric.     

Preparation,Infrared Emissivity,and Dielectric and Microwave Absorption Properties of Fe-Doped ZnO Powder

Fe-doped ZnO powders have been synthesized by the coprecipitation method using zinc nitrate [Zn(NO₃)₂·6H₂O] as starting material, urea [CO(NH₂)₂] as precipitator, and ferric nitrate [Fe(NO₃)₃·9H₂O] as doping source. The microstructure of the prepared powders has been characterized by x-ray diffraction and scanning electron microscopy. Results show that, when the molar ratio of Fe to (Zn + Fe) was less than 0.09, the prepared powder was ZnO(Fe) solid solution, and the ZnFe₂O₄ impurity phase appeared when the Fe doping content was further increased. The electric permittivity in the frequency range of 8.2 GHz to 12.4 GHz and the average infrared emissivity in the wavelength range of 8 μm to 14 μm have been determined for the prepared powders. The average infrared emissivity decreased with increasing Fe doping content. The real (ε′) and imaginary part (ε″) of the permittivity of the prepared powders showed opposite trends. When the molar ratio of Fe to (Zn + Fe) was 0.03, the prepared Fe-doped ZnO powder demonstrated the best microwave absorption in the frequency range of 8.2 GHz to 12.4 GHz.     

竹节形碳纳米管的制备

采用乙醇催化燃烧法制备竹节形碳纳米管，利用乙醇作为碳源和燃料提供材料生长所需的能量，以Cu薄片作为基底，FeCl3与Fe（NO3）3作为催化剂先体。通过扫描电子显微镜（SEM）、透射电子显微镜（TEM）、喇曼光谱对黑色絮状的沉积产物进行表征。实验结果表明，产物中的碳纳米管具有较好的竹节形结构，竹节形碳纳米管的形貌和微结构与独特的制备条件有关。并对竹节形碳纳米管的生成机理进行了初步探讨。     

Influence of ZnO Inclusions on the Low-Temperature Thermoelectric Properties of CoSb3

CoSb₃ composites with different amounts of ZnO nanoparticles (2?wt.% to 12?wt.%) were prepared from nanosized ZnO (commercial) and micron-sized CoSb₃ (obtained via solid-state reaction) particles mixed in solution and freeze dried. The resulting powders were densified by spark plasma sintering. The samples were characterized by x-ray diffraction and scanning electron microscopy. It was found that ZnO forms micron-sized clusters at the grain boundaries of the matrix material. The thermoelectric properties (electrical resistivity, thermopower, and thermal conductivity) were measured in the 2?K to 300?K temperature range. Both the electrical and thermal conductivities were observed to decrease with increasing ZnO content. The dimensionless figure of merit ZT was improved by up to 30% at 300?K for the sample containing 2?wt.% ZnO.     

Low-Temperature Synthesis and Thermoelectric Properties of n-Type PbTe

n-Type PbTe compounds were synthesized at temperatures as low as 430°C. After synthesis, the materials were ground, cold pressed, and sintered at 600°C. The effect of this low-temperature synthesis on the structural features and thermoelectric properties of as-prepared and PbI₂-doped materials was investigated for the first time. The Seebeck coefficient, and electrical and thermal conductivity were measured in the temperature range 2 K ≤ T ≤  610 K. The results show that all materials exhibit n-type conduction and the thermoelectric properties are improved by doping. ZT values reach 0.5 at 610 K, and the discrepancies with the literature are discussed.     

ZnO Thin Film, Device, and Circuit Fabrication using Low-Temperature PECVD Processes

We report undoped ZnO films deposited at low temperature (200°C) using plasma-enhanced chemical vapor deposition (PECVD). ZnO thin-film transistors (TFTs) fabricated using ZnO and Al₂O₃ deposited in situ by PECVD with moderate gate leakage show a field-effect mobility of 10 cm²/V s, threshold voltage of 7.5 V, subthreshold slope <1 V/dec, and current on/off ratios >10⁴. Inverter circuits fabricated using these ZnO TFTs show peak gain magnitude (dV _out/dV _in) ~5. These devices appear to be strongly limited by interface states and reducing the gate leakage results in TFTs with lower mobility. For example, ZnO TFTs fabricated with low-leakage Al₂O₃ have mobility near 0.05 cm²/V s, and five-stage ring-oscillator integrated circuits fabricated using these TFTs have a 1.2 kHz oscillation frequency at 60 V, likely limited by interface states.     

Low-Temperature Preparation of Undoped ZnO Films with High Transparency and Conductivity by Ion Beam Deposition

Low-temperature growth of undoped ZnO films with high transparency and low electrical resistance was performed by ion beam sputtering. After systematic testing, resistivity as low as 2.95 × 10⁻³ Ω cm was obtained at a substrate temperature of 150°C, ion source voltage of 850 V, and ion beam current of 30 mA. The transmittance of the ZnO films was in the range of 85% to 90%. Hall measurements showed that a high mobility of 21.41 cm²/Vs was obtained for films less than 200 nm thick. The related microstructures and physical properties were measured and are discussed.     

采用丙酮催化燃烧法制备多壁碳纳米管

为了探索一种简单而有效的制备多壁碳纳米管的方法,以丙酮为碳源,硝酸镍为催化剂先体,通过催化燃烧工艺在铜薄片基底上制备了多壁碳纳米管.采用扫描电子显微镜、透射电子显微镜、拉曼光谱仪对样品进行表征.结果表明,采用丙酮催化燃烧工艺合成出了多壁碳纳米管.通过拉曼光谱分析,估算了样品中的缺陷含量.该实验方法较之其它方法具有实验装置简单、易于操作、实验成本低、制备周期短等特点.     

碳纳米管的大面积合成及磁性(英文)

通过溶胶凝胶法和氢气还原法制备出Co纳米颗粒并以此作为催化剂材料,通过催化裂解苯的方法,实现了较低温度(460℃)下在Co纳米颗粒表面上合成碳纳米管。采用X射线衍射、激光喇曼光谱、场发射扫描电镜、透射电子显微镜和振动样品磁强计对所合成的碳纳米材料进行了表征。通过优化实验参数,可制备出最大产率和纯度分别为约50和98.02%(质量分数)的碳纳米管。由于铁磁性Co纳米颗粒的进入,使得整个复合物表现出比较好的磁性能。和以往以苯作为碳源合成碳纳米材料相比,此合成方案简单、成本低,且对环境无任何危害,非常适用于磁性碳纳米复合物的批量合成。     

碳纳米管的制备、修饰及其应用

简要介绍了碳纳米管的制备及其纯化技术，以及近年来碳纳米管修饰、管内填充方面的研究，并概述了碳纳米管在复合材料、发光材料、纳米器件方面的应用及其在固体基片上的定向组装。     

ZnO Nanowires,Nanotubes, and Complex Hierarchical Structures Obtained by Electrochemical Deposition

Increasing the aspect ratio of ZnO nanostructures is one possible strategy to improve their thermoelectric properties. ZnO nanostructures with one-dimensional (1D) and three-dimensional (3D) morphologies were obtained using electrochemical deposition. Adjusting various deposition parameters made it possible to obtain arrays of vertically aligned ZnO nanowires (NWs) with controlled dimensions, density, and electrical properties. The concentrations of zinc or chloride ions in the solution were found to be key parameters. ZnO NWs were transformed into ZnO nanotubes (NTs), with an increased aspect ratio compared with the NWs, by selectively dissolving the core of the ZnO NWs in a concentrated KCl solution. The aspect ratio was strongly increased when the ZnO NWs were hierarchically organized in a 3D morphology. The synthesis of thin films composed of ordered hollow urchin-like ZnO NW structures was performed by combining the electrochemical deposition and polystyrene sphere templating methods. The electronic properties of the urchin-like ZnO structures were investigated by means of photoluminescence and transmission measurements.     

螺旋碳纳米管的制备、表征及性能

采用溶胶-凝胶结合氢气还原方法制备了Ni纳米颗粒,并用这种Ni纳米颗粒作为催化剂,通过催化裂解乙炔的方法在425℃制备了螺旋度较高且呈对称生长的螺旋碳纳米管。结果表明,本方法简单、成本低、环境友好,可大量制备高纯度螺旋碳纳米管。场发射扫描电镜(FE-SEM)及高分辨透射电镜(HR-TEM)图片表明,通常情况下两根旋向相反的螺旋碳纳米管生长在一个催化剂颗粒上,且这种纳米螺旋呈空心管状。X射线衍射及拉曼光谱分析表明,所得样品成分为有缺陷的石墨结构和镍多晶,未发现其他杂相。此外,对样品的磁性及微波吸收性能进行了研究。     

基于微流体的ZnO纳米线的合成

微流控芯片在纳米材料的合成方面具有突出的优势,在芯片中通过微流体的操控制备ZnO纳米线,并利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)和能谱仪(EDS)对制备得到的ZnO纳米线的表面形貌、晶体结构及成分进行表征。实验结果表明,在具有微腔室结构的微通道中可以构建浓度梯度,从而在单一通道中制备得到形貌及尺寸不同的致密ZnO纳米线,成为高效探索纳米材料合成条件的便捷手段。分别以玻璃片、ZnO种子层和ZnO纳米线为载体,对异硫氰酸荧光素标记的羊抗牛IgG抗体进行荧光检测,发现ZnO纳米线可显著增强荧光信号。     

Synthesis and Properties of Mg-doped ZnO Nanobelts

The chemical vapor deposition(CVD)growth method is applicable to produce high-yield single-crystalline ZnO nanobelts.The Mg-doped ZnO nanobelts with a smooth surface have been successfully synthesized.The morphology,microstructure and optical properties of the ZnO nanobelts were analyzed by X-ray diffraction(XRD),scanning electron microscope(SEM),transmission electron microscope(TEM),selective area electron diffraction(SAED),energy dispersive X-ray spectroscopy(EDS)and photoluminescence(PL)spectroscopy.Resu...     

Microwave Magnetoabsorption Oscillations in Fe-Doped HgSe Crystals

Magnetoresistance oscillations are considered in the case of microwave-radiation absorption in HgSe samples with a different Fe-impurity concentration. From the simultaneous analysis of the field and temperature dependences of the Shubnikov–de Haas oscillations, the effective mass, the Dingle temperature, and the quantum-limit field corresponding to the Fermi level are obtained. A method for analyzing the spectra with several oscillation frequencies, i.e., the beating effect, is proposed. The results are compared with data obtained by Hall measurements.     

定向SnO_2纳米管的阵列制备及其场发射性能

SnO2纳米材料由于其优异的性能和在纳米电子器件以及气敏传感器等方面的潜在应用受到了广泛关注,快速大量制备SnO2纳米管(线)是其规模化应用的前提。利用自制的高频感应设备在Si基底上快速生长出定向的SnO2纳米管阵列,由SEM和TEM分析可知,SnO2纳米管直径达到50～100nm。场发射结果表面制备的SnO2纳米管阵列具有较低的开启电压,即当产生的电流密度为10μA/cm2时所对应的电场只有1.64V/μm,这一数值低于碳纳米管和其他一维氧化物纳米材料的开启电场,同时所制备的产物具有良好的场发射稳定性,良好的场发射性能说明SnO2纳米管在场发射平板显示及真空电子器件方面具有较好的应用潜力。     

Synthesis of sulfur-doped ZnO nanowires by electrochemical deposition

Sulfur-doped zinc oxide (ZnO) nanowires have been successfully synthesized by an electric field-assisted electrochemical deposition in porous anodized aluminum oxide template at room temperature. X-ray diffraction and the selected area electron diffraction results show that the as-synthesized nanowires are single crystalline and have a highly preferential orientation. Transmission electron microscopy observations indicate that the nanowires are uniform with an average diameter of 70 nm and length up to several tens of micrometers. X-ray photoelectron spectroscopy further reveals the presence of S in the ZnO nanowires. Room-temperature photoluminescence is observed in the doped ZnO nanowires, which exhibits a violet emission and blue emissions besides the typical photoluminescence spectrum of a single crystal ZnO.     

多糖绿色合成纳米氧化锌的研究

利用一种高分子多糖——葡聚糖作为稳定剂和软模板,通过一条绿色途径合成了粒径为70nm左右的纳米氧化锌,发现其在380nm处有一个强烈的吸收峰。通过SEM,TEM等测试手段,研究了葡聚糖分子以及热处理对纳米氧化锌形貌和粒径的影响,并探讨了纳米氧化锌的形成机理。此种方法也可拓展到其它纳米氧化物的合成领域。     

氧化锌压敏电阻用掺杂粉体的水热合成

以氧化锌为原料,添加其它掺杂金属氧化物,在水热高温、高压下一次性合成ZnO压敏电阻用掺杂粉体,利用SEM和XRD研究了前驱体配比、水热温度、反应介质对掺杂氧化锌生长的影响,用此掺杂氧化锌粉体制备的ZnO压敏电阻的非线性系数达到43.48。     

Cu掺杂ZnO薄膜的结构及发光特性

采用溶胶-凝胶旋涂法在玻璃衬底上制备了不同Cu掺杂量的ZnO薄膜。用显微镜和X射线衍射(XRD)研究了Cu掺杂对ZnO薄膜形貌和微结构的影响。结果表明,制备得到的ZnO薄膜具有应变小和c轴择优取向。室温下测量了样品Zn1-xCuxO的光致发光(PL)谱,发现所有样品的PL谱中均观察到435nm左右的蓝光发光带,发光带强度与Cu的掺杂量有关;当x=0.06时,Zn1-xCuxO薄膜的PL谱中出现了较强的蓝光发射。分析了掺杂量对发光性能的影响,并对样品的发光机制进行了探讨,推断出蓝光峰来源于电子由导带底到锌空位(VZn)能级的跃迁及锌填隙(Zni)能级到价带顶的跃迁,它们可通过改变Cu的掺杂量予以控制。