Crystallization of amorphous silicon beyond the crystallized polycrystalline silicon region induced by metal nickel

Crystallization of amorphous silicon（a-Si） which starts from the middle of the a-Si region separating two adjacent metal-induced crystallization（MIC） polycrystalline silicon（poly-Si） regions is observed. The crystallization is found to be related to the distance between the neighboring nickel-introducing MIC windows. Trace nickel that diffuses from the MIC window into the a-Si matrix during the MIC heat-treatment is experimentally discovered, which is responsible for the crystallization of the a-Si beyond the MIC front. A minimum diffusion coefficient of 1.84×10^-9cm^2/s at 550℃ is estimated for the trace nickel diffusion in a-Si.

Degradation and its fast recovery in a-IGZO thin-film transistors under negative gate bias stress

A new type of degradation phenomena featured with increased subthreshold swing and threshold voltage after negative gate bias stress(NBS)is observed for amorphous InGaZnO(a-IGZO)thin-film transistors(TFTs),which can recover in a short time.After comparing with the degradation phenomena under negative bias illumination stress(NBIS),positive bias stress(PBS),and positive bias illumination stress(PBIS),degradation mechanisms under NBS is proposed to be the generation of singly charged oxygen vacancies(V_(o)^(+))in addition to the commonly reported doubly charged oxygen vacancies(V_(o)^(2+)).Furthermore,the NBS degradation phenomena can only be observed when the transfer curves after NBS are measured from the negative gate bias to the positive gate bias direction due to the fast recovery of V_(o)^(+)under positive gate bias.The proposed degradation mechanisms are verified by TCAD simulation.

Degradation mechanisms for polycrystalline silicon thin-film transistors with a grain boundary in the channel under negative gate bias stress

The negative gate bias stress(NBS)reliability of n-type polycrystalline silicon(poly-Si)thin-film transistors(TFTs)with a distinct defective grain boundary(GB)in the channel is investigated.Results show that conventional NBS degradation with negative shift of the transfer curves is absent.The on-state current is decreased,but the subthreshold characteristics are not affected.The gate bias dependence of the drain leakage current at V_(ds)of 5.0 V is suppressed,whereas the drain leakage current at V_(ds)of 0.1 V exhibits obvious gate bias dependence.As confirmed via TCAD simulation,the corresponding mechanisms are proposed to be trap state generation in the GB region,positive-charge local formation in the gate oxide near the source and drain,and trap state introduction in the gate oxide.

A systematic study of light dependency of persistentphotoconductivity in a-InGaZnO thin-film transistors

Persistent photoconductivity(PPC)effect and its light-intensity dependence of both enhancement and depletion(E-/D-)mode amorphous InGaZnO(a-IGZO)thin-film transistors(TFTs)are systematically investigated.Density of oxygen vacancy(V O)defects of E-mode TFTs is relatively small,in which formation of the photo-induced metastable defects is thermally activated,and the activation energy(E a)decreases continuously with increasing light-intensity.Density of V O defects of D-mode TFTs is much larger,in which the formation of photo-induced metastable defects is found to be spontaneous instead of thermally activated.Furthermore,for the first time it is found that a threshold dose of light-exposure is required to form fully developed photo-induced metastable defects.Under low light-exposure below the threshold,only a low PPC barrier is formed and the PPC recovery is fast.With increasing the light-exposure to the threshold,the lattice relaxation of metal cations adjacent to the doubly ionized oxygen vacancies(V O^2+)is fully developed,and the PPC barrier increases to∼0.25 eV,which remains basically unchanged under higher light-exposure.Based on the density of V O defects in the channel and the condition of light illumination,a unified model of formation of photo-induced metastable defects in a-IGZO TFTs is proposed to explain the experimental observations.

Degradation mechanisms for a-InGaZnO thin-film transistors functioning under simultaneous DC gate and drain biases

Degradation of a-InGaZnO thin-film transistors working under simultaneous DC gate and drain bias stress is investigated,and the corresponding degradation mechanism is proposed and verified.The maximum degradation occurs under the bias stress condition that makes the electric field and electron concentration relatively high at the same time.Trapping of hot electrons in the etching-stop layer under the extended drain electrode is proven to be the underlying mechanism.The observed degradation phenomena,including distortion in the transfer curve on a logarithmic scale and two-slope dependence on gate bias on a linear scale,current crowding in the output curve,and smaller degradation in transfer curves measured under large drain bias,can all be well explained with the proposed degradation mechanism.

直肠黏膜环切联合阴道后壁折叠治疗出口梗阻型便秘的效果观察

目的观察直肠黏膜环切联合阴道后壁折叠治疗出口梗阻型便秘(ODS)的效果。方法回顾性分析2021年1月至2022年6月石家庄市人民医院收治的75例直肠前突所致ODS女性患者临床资料,根据手术方法将患者分为单纯组(直肠黏膜环切治疗)35例和联合组(直肠黏膜环切联合阴道后壁折叠治疗)30例,对比两组患者治疗效果,包括手术相关指标、直肠前突深度、症状严重度评分(Longo ODS)及术后并发症发生情况及复发率。结果联合组手术时间长于单纯组(P<0.05),术中出血量多于单纯组(P<0.05),住院时间及创面愈合时间与单纯组比较,差异均无统计学意义(P>0.05)。术后6、12个月,两组直肠前突深度均减小(P<0.05),联合组直肠前突深度均小于单纯组(P<0.05);两组Longo ODS评分均降低(P<0.05),联合组评分均低于单纯组(P<0.05)。联合组并发症发生率与单纯组比较,差异无统计学意义(P>0.05)。联合组的复发率低于单纯组(P<0.05)。结论直肠黏膜环切联合阴道后壁折叠治疗ODS效果较好,可以显著改善患者直肠前突形态,调节其排便功能。

Finite element analysis of temperature distribution of polycrystalline silicon thin film transistors under self-heating stress

The temperature distribution of typical n-type polycrystalline silicon thin film transistors under selfheating(SH)stress is studied by finite element analysis.From both steady-state and transient thermal simulation,the influence of device power density,substrate material,and channel width on device temperature distribution is analyzed.This study is helpful to understand the mechanism of SH degradation,and to effectively alleviate the SH effect in device operation.