化学处理增强碳纳米管的湿敏效应

研究了多壁碳纳米管的湿敏效应。研究中所用碳纳米管是用热灯丝化学汽相沉积法生长的。实验结果表明，经由化学修饰后碳纳米管的湿敏效应有了极大的增强。化学修饰后碳纳米管在水蒸汽中电阻相对变化达到了300％，而未修饰只有3．25％。本文对其结果进行了分析和讨论。     

化学处理增强碳纳米管的湿敏效应

研究了多壁碳纳米管的湿敏效应.研究中所用碳纳米管是用热灯丝化学汽相沉积法生长的.实验结果表明,经由化学修饰后碳纳米管的湿敏效应有了极大的增强.化学修饰后碳纳米管在水蒸汽中电阻相对变化达到了300%,而未修饰只有3.25%.本文对其结果进行了分析和讨论.     

SnO2薄膜的湿敏效应

报道了用喷雾热分解法在不同温度下制备二氧化锡薄膜,发现其在３２５℃时已晶化,得到四方相多晶ＳｎＯ２。这种薄膜具有明显湿敏效应。测量表明,较高湿度区阻值随湿度变化近似线性,从高湿到低湿平均为每上升１％ＲＨ,阻值下降８．８π,响应速度小于１分钟,阻值恢复较容易。     

半导体湿敏器件及其应用

介绍了半导体湿敏器件的基本分类和性能，提出了应用湿敏器件的应注意的有关问题，详述了三种实用测湿，控湿电路。     

Pt/TiO_2二极管湿敏传感器

Pt常被用来在金属氧化物半导体上做肖特基接触.在常温下,Pt/TiO2界面处的电子电导对Pt/TiO2肖特基势垒高度的变化非常敏感.本文描述了利用该性质制造的湿敏传感器的性能,并讨论了因水在Pt/TiO2界面处的化学吸附,引起表面态费米能级改变,影响Pt/TiO2肖特基势垒的高度,从而导致了I-V曲线的变化的物理过程,对器件制造过程中的工艺问题也有所论述     

怎样选用元器件讲座（十九）湿敏元件

湿度,是一个与人类关系密切的物理量。传统的毛发湿度计和干湿球湿度计,已不能适应现代的需要,而半导体湿敏元件正在悄然进入现代家庭,成为家庭电子     

Synthesis of carbon nanotubes by catalytic chemical vapour deposition: A review on carbon sources,catalysts and substrates

Carbon nanotubes (CNTs) have been extensively studied during the past two decades and Catalytic Chemical Vapour Deposition (CCVD) technique has been untiredly employed by researchers to produce CNTs of various crystallographic configurations. In this paper the material aspects carbon sources, catalysts and substrates with regard to CCVD synthesis of carbon nanotubes are reviewed in light of latest developments and understandings in the field. The role of these materials in synthesis of CNTs is explained keeping the upto date literature in view. Latest research reports and their findings are presented with regard to effects of growth control aspects such as temperature, vapour pressure and catalyst concentration on CNT formation. Besides recent understandings with regard to preferential growth of CNTs are also discussed. From this literature review it is found that carbon diffusibility and carbon solubility of any catalyst are two important factors in determining CNT nucleation and growth. Moreover, addition of catalyst species to any transition metal catalyst can improve the catalyst performance and addition of water, air, alcohol etc. during CCVD process can increase the activity and lifetime of the catalyst besides enhances the production of CNTs.     

RF-PECVD法研究碳纳米管的生长特性

采用射频等离子体增强化学气相沉积(RF-PECVD),以Fe作为催化剂,在Si基片上生长了碳纳米管(CNT),采用扫描电子显微镜(SEM),高分辨透射电子显微镜(HR TEM)以及显微Raman光谱等对制备的CNT的形貌及结构进行了表征.结果表明:700℃和800℃温度下生长的CNT均取向无序、弯曲缠结,由整齐排列的圆...     

Effect of electrode material on transport and chemical sensing characteristics of metal/carbon nanotube contacts

In this paper, we report on the electrical transport characteristics and sensitivity to chemical exposure of single wall carbon nanotube devices fabricated on Pd, plasma-oxidized Pd, and Au electrodes. When the devices are exposed to vapors from ammonia, ethanol, and water, the response of current to each chemical is unique. However, there is essentially no difference in response between devices with different electrode materials. This finding suggests that for the chemical species tested in this study, the main interaction is on the nanotube or nanotube junction, and not on the effect stemming from electrode adsorption and the change in electrode work function.     

Ni/MgO催化剂下碳纳米管的生长特性

采用射频等离子体增强化学气相沉积法(RF-PECVD),以Ni/MgO为催化剂,在Si基片上生长了碳纳米管,采用X射线衍射(XRD)、扫描电镜(SEM)、Raman光谱以及高分辨透射电镜(HRTEM)等对不同的MgO含量下制备的碳纳米管形貌及结构进行了表征。结果表明,随着MgO含量的增加,从碳纳米洋葱转化为碳纳米管,其直径逐渐变小、均匀,碳纳米管纯度提高,结晶性能越好;碳纳米管顶端形成开口或闭口的碳洋葱纳米结构,而管的主干区域则存在催化剂,并且随着MgO含量的增加,呈现纳米颗粒转化为纳米线的趋势;MgO含量为50%时,部分碳纳米管的外壁剥离,形成了单原子石墨层,长度达到7nm,并在碳纳米管内部填充了Ni纳米线,其长度有60nm。     

Enhanced field emission and hysteresis characteristics of aligned carbon nanotubes with Ti decoration

The field emission behavior of aligned carbon nanotubes (CNTs) is remarkably improved by decorating their surfaces with Ti nanoparticles through a sputtering process. The CNT/Ti(4 nm) sample shows a low turn-on field of 0.63 V/μm at 10 μA/cm², low threshold field of 1.06 V/μm at 1 mA/cm², and maximum field emission current density of 23 mA/cm² at 1.80 V/μm. The enhanced field emission properties of the CNT/Ti samples are attributed to the added defect sites and Ti nanoparticles, which increase the field enhancement factor and density of emission sites. Stability measurements indicate that the Ti coating, which acts as a protective layer, also strengthens the field emission stability of the CNT arrays. Moreover, the extent of hysteresis in the current–voltage sweep highly depends on the voltage-sweep speed.     

图案化定向碳纳米管阵列的场发射性能研究

考虑到碳纳米管的几何形貌会在一定程度上影响其场发射性能,如驱动电场,发射电流强度等,因此本文设计了三种不同的几何图案,并采用热气相化学沉积（TCVD）法制备出了相应几何结构的定向碳纳米管阵列;通过模拟计算和场发射测试实验,我们对以上三种结构的场发射性能进行比较,发现具有规则六边形蜂窝形状的碳纳米管阵列具有最强的边缘效应,最小的屏蔽效应,以及相同电场下最大的发射电流。     

乙醇化学气相沉积法制备多壁碳纳米管

介绍了采用浮动催化剂法，利用乙醇化学气相沉积法制备多壁碳纳米管。采用二茂铁作为催化剂先体，乙醇作为碳源，利用石英基底收集产物。催化剂先体二茂铁的蒸汽在载气的作用下被带到高温区（800℃），二茂铁在高温区分解形成铁纳米催化剂颗粒，这些催化剂颗粒催化生长出多壁碳纳米管。利用扫描电子显微镜、（高分辨）透射电子显微镜对制备的多壁碳纳米管都进行了表征。实验结果表明，制备的多壁碳纳米管均匀性好，石墨化程度较高。     

Chemical vapor deposition synthesis of self-aligned carbon nanotube arrays

A procedure for producing arrays of self-aligned carbon nanotubes (CNTs) using standard chemical vapor deposition (CVD) is reported. Using UV photolithography, silicon substrates are patterned with a thin layer of thermally evaporated iron as a CNT catalyst. The CVD synthesis was carried out over a small temperature range (700°C–800°C) using acetylene and methane gasses, producing aligned CNT towers. Scanning electron microscopy (SEM) analysis shows a relationship between CNT tower height and synthesis time. Additionally, results show that impurity particles dramatically effect CNT tower growth. These results indicate that aligned CNTs can be produced in a desired pattern with height control.     

乙醇化学气相沉积法制备多壁碳纳米管

介绍了采用浮动催化剂法,利用乙醇化学气相沉积法制备多壁碳纳米管。采用二茂铁作为催化剂先体,乙醇作为碳源,利用石英基底收集产物。催化剂先体二茂铁的蒸汽在载气的作用下被带到高温区(800℃),二茂铁在高温区分解形成铁纳米催化剂颗粒,这些催化剂颗粒催化生长出多壁碳纳米管。利用扫描电子显微镜、(高分辨)透射电子显微镜对制备的多壁碳纳米管都进行了表征。实验结果表明,制备的多壁碳纳米管均匀性好,石墨化程度较高。