The grain boundaries （GBs） have a strong effect on the electric properties of ZnO thin film transistors （TFTs）. A novel grain boundary model was developed to analyse the effect. The model was characterized with di...The grain boundaries （GBs） have a strong effect on the electric properties of ZnO thin film transistors （TFTs）. A novel grain boundary model was developed to analyse the effect. The model was characterized with different angles between the orientation of the grain boundary and the channel direction. The potential barriers formed by the grain boundaries increase with the increase of the grain boundary angle, so the degradation of the transistor characteristics increases. When a grain boundary is close to the drain edge, the potential barrier height reduces, so the electric properties were improved.展开更多
The dependence of transistor characteristics on grain boundary （GB） position in short-channel ZnO thin film transistors （TFTs） has been investigated using two-dimensional numerical simulations. To simulate the dev...The dependence of transistor characteristics on grain boundary （GB） position in short-channel ZnO thin film transistors （TFTs） has been investigated using two-dimensional numerical simulations. To simulate the device accurately, both tail states and deep-level states are taken into consideration. It is shown that both the transfer and output characteristics of ZnO TFTs change dramatically with varying GB position, which is different from polycrystalline Si （poly-Si） TFTs. By analysing the mechanism of the carrier transportation in the device, it is revealed that the dependence is derived from the degrees of carrier concentration descent and mobility variation with CB position.展开更多
A novel grain boundary(GB) model characterized with different angles and positions in the nanowire was set up.By means of device simulator,the effects of grain boundary angle and location on the electrical performance...A novel grain boundary(GB) model characterized with different angles and positions in the nanowire was set up.By means of device simulator,the effects of grain boundary angle and location on the electrical performance of ZnO nanowire FET(Nanowire Field-Effect Transistor) with a wrap-around gate configuration,were explored.With the increase of the grain boundary angle,the electrical performance degrades gradually.When a grain boundary with a smaller angle,such as 5° GB,is located close to the source or drain electrode,the grain boundary is partially depleted by an electric field peak,which leads to the decrease of electron concentration and the degradation of transistor characteristics.When the 90° GB is located at the center of the nanowire,the action of the electric field is balanced out,so the electrical performance of transistor is better than that of the 90° GB located at the other positions.展开更多
We established a model for investigating polycrystalline silicon（poly-Si） thin film transistors（TFTs）.The effect of grain boundaries（GBs） on the transfer characteristics of TFT was analyzed by considering the nu...We established a model for investigating polycrystalline silicon（poly-Si） thin film transistors（TFTs）.The effect of grain boundaries（GBs） on the transfer characteristics of TFT was analyzed by considering the number and the width of grain boundaries in the channel region,and the dominant transport mechanism of carrier across grain boundaries was subsequently determined.It is shown that the thermionic emission（TE） is dominant in the subthreshold operating region of TFT regardless of the number and the width of grain boundary.To a poly-Si TFT model with a 1 nm-width grain boundary,in the linear region,thermionic emission is similar to that of tunneling（TU）,however,with increasing grain boundary width and number,tunneling becomes dominant.展开更多
C-oriented ZnO epitaxial thin films are grown separately on the a-plane and c-plane sapphire substrates by using a molecular-beam epitaxy technique. In contrast to single crystalline ZnO films grown on a-plane sapphir...C-oriented ZnO epitaxial thin films are grown separately on the a-plane and c-plane sapphire substrates by using a molecular-beam epitaxy technique. In contrast to single crystalline ZnO films grown on a-plane sapphire, the films grown on c-plane sapphire are found to be bi-crystalline; some domains have a 30~ rotation to reduce the large mismatch between the film and the substrate. The presence of these rotation domains in the bi-crystalline ZnO thin film causes much more carrier scatterings at the boundaries, leading to much lower mobility and smaller mean free path of the mobile carriers than those of the single crystalline one. In addition, the complex impedance spectra are also studied to identify relaxation mechanisms due to the domains and/or domain boundaries in both the single crystalline and bi-crystalline ZnO thin films.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos 50677014,50602014 and 10874042)the National High Technology Joint Research Program of China (Grant No 2006AA04A104)the Science-Technology Foundation of Hunan Province of China (Grant Nos 2008RS4003 and 07jj107)
文摘The grain boundaries （GBs） have a strong effect on the electric properties of ZnO thin film transistors （TFTs）. A novel grain boundary model was developed to analyse the effect. The model was characterized with different angles between the orientation of the grain boundary and the channel direction. The potential barriers formed by the grain boundaries increase with the increase of the grain boundary angle, so the degradation of the transistor characteristics increases. When a grain boundary is close to the drain edge, the potential barrier height reduces, so the electric properties were improved.
基金Project supported by the National Natural Science Foundation of China (Grant No. 50872112)NPU Foundation for Fundamental Research,China (Grant No. JC201017)
文摘The dependence of transistor characteristics on grain boundary （GB） position in short-channel ZnO thin film transistors （TFTs） has been investigated using two-dimensional numerical simulations. To simulate the device accurately, both tail states and deep-level states are taken into consideration. It is shown that both the transfer and output characteristics of ZnO TFTs change dramatically with varying GB position, which is different from polycrystalline Si （poly-Si） TFTs. By analysing the mechanism of the carrier transportation in the device, it is revealed that the dependence is derived from the degrees of carrier concentration descent and mobility variation with CB position.
基金Project(60876022) supported by the National Natural Science Foundation of ChinaProject(50925727) supported by the National Natural Science Funds for Distinguished Young Scholars of China
文摘A novel grain boundary(GB) model characterized with different angles and positions in the nanowire was set up.By means of device simulator,the effects of grain boundary angle and location on the electrical performance of ZnO nanowire FET(Nanowire Field-Effect Transistor) with a wrap-around gate configuration,were explored.With the increase of the grain boundary angle,the electrical performance degrades gradually.When a grain boundary with a smaller angle,such as 5° GB,is located close to the source or drain electrode,the grain boundary is partially depleted by an electric field peak,which leads to the decrease of electron concentration and the degradation of transistor characteristics.When the 90° GB is located at the center of the nanowire,the action of the electric field is balanced out,so the electrical performance of transistor is better than that of the 90° GB located at the other positions.
基金Funded by the National Natural Science Foundation of China(Nos.51202063 and 51177003)Hubei Provincial Department of Education(No.Q20111009)
文摘We established a model for investigating polycrystalline silicon（poly-Si） thin film transistors（TFTs）.The effect of grain boundaries（GBs） on the transfer characteristics of TFT was analyzed by considering the number and the width of grain boundaries in the channel region,and the dominant transport mechanism of carrier across grain boundaries was subsequently determined.It is shown that the thermionic emission（TE） is dominant in the subthreshold operating region of TFT regardless of the number and the width of grain boundary.To a poly-Si TFT model with a 1 nm-width grain boundary,in the linear region,thermionic emission is similar to that of tunneling（TU）,however,with increasing grain boundary width and number,tunneling becomes dominant.
基金partially supported by the National Natural Science Foundation of China (Grant No. 10804017)the Natural Science Foundation of Jiangsu Province of China (Grant No. BK2007118)+3 种基金the Research Fund for the Doctoral Program of Higher Educa-tion of China (Grant No. 20070286037)the Cyanine-Project Foundation of Jiangsu Province of China (Grant No. 1107020060)the Foundation for Climax Talents Plan in Six-Big Fields of Jiangsu Province of China (Grant No. 1107020070)the New Century Excellent Talents in University (Grant No. NCET-05-0452)
文摘C-oriented ZnO epitaxial thin films are grown separately on the a-plane and c-plane sapphire substrates by using a molecular-beam epitaxy technique. In contrast to single crystalline ZnO films grown on a-plane sapphire, the films grown on c-plane sapphire are found to be bi-crystalline; some domains have a 30~ rotation to reduce the large mismatch between the film and the substrate. The presence of these rotation domains in the bi-crystalline ZnO thin film causes much more carrier scatterings at the boundaries, leading to much lower mobility and smaller mean free path of the mobile carriers than those of the single crystalline one. In addition, the complex impedance spectra are also studied to identify relaxation mechanisms due to the domains and/or domain boundaries in both the single crystalline and bi-crystalline ZnO thin films.
