双极性传输特性是制约碳纳米管场效应管(carbon nanotube field effect transistors,CNFETs)性能提高的一个重要因素.为降低器件的双极性传输特性并获得较大的开关电流比,提出了一种漏端梯度掺杂策略,该策略不仅适合于类MOS碳纳米管场效应管(C-CNFETs),同时也适合于隧穿碳纳米管场效应管(T-CNFETs).基于非平衡格林函数的数值研究结果表明,该策略不仅能有效降低器件的双极传输特性,而且能将器件开关电流比提高数个数量级.进一步研究发现,该掺杂策略在这两类碳纳米管场效应管器件结构中的应用存在诸多差异:C-CNFETs中可能发生的能级钳制将削弱器件导通状态性能,而T-CNFETs中无此现象;C-CNFETs中源、漏两端均采用梯度掺杂能进一步提高器件性能,而该策略并不适于T-CNFETs;梯度掺杂后的T-CNFETs器件性能受轻度掺杂区域宽度的影响较C-CNFETs更为显著.同时,该梯度掺杂策略会造成一定的面积开销,因此在实际应用中应合理选取器件结构、掺杂浓度、掺杂区域宽度等参数,以获得速度、功耗与面积之间的最佳折中.
The electrical characteristics of Pt-ZnO Schottky nano-contact have been studied. Well aligned ZnO nanorod arrays were synthesized by two-step wet-chemical method. A Pt-coated conducting probe of atomic force microscope was placed on the head face of the ZnO nanorod, thereby forming a Pt-ZnO nano-contact. The I-V characteristic curve shows that the Pt-ZnO nano-contact exhibits rectifying effect, like a Schottky diode with an ideality factor of 3.2 and a reverse-bias breakdown voltage more than -10 V. The study suggests that a high electric field is induced on the ZnO beneath the contact point when a bias voltage is applied, hence, the Schottky barrier thickness is decreased, and results in easier tunneling across the Pt-ZnO interface and a large ideality factor.
SHAO ZhengZheng , ZHANG XueAo, WANG XiaoFeng & CHANG ShengLi Center of Materials Science, College of Science, National University of Defense Technology, Changsha 410073, China
Periodic disposed quantum dot arrays are very useful for the large scale integration of single electron devices. Gold quantum dot arrays were self-assembled inside pore channels of ordered amino-functionalized mesoporous silica thin films, employing the neutralization reaction between chloroauric acid and amino groups. The diameters of quantum dots are controlled via changing the aperture of pore channels from 2.3 to 8.3 nm, which are characterized by HRTEM, SEM and FT-IR. UV-vis absorption spectra of gold nanoparticle/mesoporous silica composite thin films exhibit a blue shift and intensity drop of the absorption peak as the aperture of mesopores decreases, which represents the energy level change of quantum dot arrays due to the quantum size effect.
