基于Si掺杂Sb2Te3薄膜的相变存储器研究

采用磁控三靶(Si,Sb及Te)共溅射法制备了Si掺杂Sb2Te3薄膜,作为对比,制备了Ge2Sb2Te5和Sb2Te3薄膜,并且采用微加工工艺制备了单元尺寸为10μm×1Oμm的存储器件原型来研究器件性能.研究表明,Si掺杂提高了Sb2Te3薄膜的晶化温度以及薄膜的晶态和非晶态电阻率,使得其非晶态与晶态电阻率之比达到106,提高了器件的电阻开/关比;同Ge2Sb2Te5薄膜相比,16at%Si掺杂Sb2Te3薄膜具有较低的熔点和更高的晶态电阻率,这有利于降低器件的RESET电流.研究还表明,采用16at%Si掺杂Sb2Te3薄膜作为存储介质的存储器器件原型具有记忆开关特性,可以在脉高3V、脉宽500 ns的电脉冲下实现SET操作,在脉高4 V、脉宽20 ns的电脉冲下实现RESET操作,并能实现反复写/擦,而采用Ge2Sb2Te5薄膜的相同结构的器件不能实现RESET操作.     

Ge2 Sb2 Te5相变薄膜光学及擦除性能研究

利用蓝绿激光对非晶态Ge2Sb2Te5 相变薄膜进行擦除性能的研究,分别用1000 ns,500 ns,100 ns,60 ns脉宽的蓝绿激光进行实验.结果表明,一定脉宽下,反射率对比度随擦除功率的增加而增大.并且,在1000 ns,500 ns,100 ns,60 ns的激光作用时间范围内,非晶态薄膜均可转变成晶态.对于脉宽为60 ns的蓝绿激光,擦除功率大于4.49 mW以后,薄膜的反射率对比度高于15％,这表明Ge2Sb2Te5相变薄膜在短脉宽、低擦除功率条件下,可具有较高的晶化速度.同时,分析了非晶态和晶态Ge2Sb2Te5相变薄膜的光谱特性,对比研究了780 nm,650 nm,514 nm和405 nm波长处的反射率和反射率对比度,提出了Ge2Sb2Te5相变薄膜用于蓝光光盘的改进方法.     

氮掺杂Ge2Sb2Te5相变存储器的多态存储功能

通过反应溅射的方法,制备了N掺杂的Ge2Sb2Te5(N-GST)薄膜,用作相变存储器的存储介质.研究表明,掺杂的N以GeN的形式存在,不仅束缚了Ge2Sb2Te5 (GST)晶粒的长大也提高了GST的晶化温度和相变温度.利用N-GST薄膜的非晶态、晶态面心立方相和晶态六方相的电阻率差异,能够在同一存储单元中存储三个状态,实现相变存储器的多态存储功能.     

溅射气压对Ge2Sb2Te5薄膜光学常数的影响

实验研究了氩气气压对溅射制备的Ge2 Sb2 Te5 薄膜的光学常数随波长变化的影响 ,结果表明 :随薄膜制备时氩气气压的增加 ,Ge2 Sb2 Te5 薄膜的折射率n先增大后减小 ,而消光系数k先减小后增大。二者都随波长的变化而变化 ,且在长波长范围变化较大 ,短波长范围变化较小 ,解释了溅射气压对Ge2 Sb2 Te5 薄膜的光学常数影响的机理     

Improvement of Electrical Properties of the Ge2Sb2Te5 Film by Doping Si for Phase-Change Random Access Memory

Si-doped Ge2Sb2Te5 films have been prepared by dc magnetron co-sputtering with Ge2Sb2Te5 and Si targets. The addition of Si in the Ge2Sb2Te5 film results in the increase of both crystallization temperature and phasetransition temperature from face-centred-cubic （fcc） phase to hexagonal （hex） phase. The resistivity of the Ge2Sb2Te5 film shows a significant increase with the Si doping. When doping 11.8 at.% of Si in the film, the resistivity after 460℃ annealing increases from 1 to 11 mΩ.cm and dynamic resistance increase from 64 to 99Ω compared to the undoped Ge2Sb2Te5 film. This is very helpful to writing current reduction of phase-change random access memory.     

热致晶化高反射率SbOx薄膜的结构分析和光学性质

利用直流磁控反应溅射法制备了SbOx薄膜,利用X射线衍射分析仪和光谱仪分别研究了这种薄膜热致晶化的微观结构和光学性质的变化,并通过非晶态薄膜粉末的示差扫描量热实验测出不同加热速度条件下结晶峰温度,研究了这种薄膜的结晶动力学。发现沉积态SbOx薄膜为非晶态,非晶态SbOx薄膜在热致晶化过程中发生了两种变化,分别对应为较低温度下Sb晶体和较高温度下立方Sb2O3相的生成。退火后晶态薄膜中出现了单质Sb和Sb2O3,300℃退火后Sb2O3相含量最大。晶态薄膜的反射率均高于沉积态,在晶态薄膜中200℃退火的薄膜反射率最大。     

高压下稳态六方Ge2Sb2Te5结构、电子和光学性质的第一性原理研究

采用基于密度泛函理论的广义梯度近似方法研究了稳态六方petrov原子序列结构Ge2Sb2Te5的结构、电子和光学性质.计算所得的平衡态晶格参数与实验数据和先前的理论结果吻合很好.基态的能带结构和态密度表明了稳态六方petrov原子序列结构的Ge2Sb2Te5持有金属性.从压强影响下体积的变化趋势发现稳态六方Ge2Sb2Te5在17 GPa和34 GPa出现不稳定,暗示在此压强下的相变发生,这与2009年Krbal等人的实验结果相吻合.同时,还系统地研究了稳态六方petrov原子序列结构的Ge2Sb2Te5高压下的光学性质,得到了高压下介电函数、吸收率、光反射率、折射率、消光系数和电子能量损失谱在20 eV内的变化情况.     

Thermal phase change and activation energy of crystallization of Ge-Sb-Te-Sn thin films

To improve the optical storage performance, Sn was doped into Ge2Sb2Te5 phase change thin films. The optical and thermal properties of Sn-doped Ge2Sb2Te5 film were investigated. The crystal structures of the as-sputtered and the annealed films were identified by the X-ray diffraction (XRD) method. The differential scanning calorimeter (DSC) method is used to get the crystallization temperature and crystallization energy (Ea). It was found that proper Sn-doping could highly improve storage performance of the Ge2Sb2Te5 media.     

Electrical Properties of Ag-Doped Ge2Sb2Te5 Films Used for Phase Change Random Access Memory

Ag-doped Ge2Sb2Te5 films were deposited by rf magnetron sputtering on SiO2/Si substrates. The content of Ag ranging from 4.5 to 11.3 at.% is determined by inductively coupled plasma atomic emission spectrometry. The crystallization temperature of Ag-doped Ge2Sb2 Te5 increases with the increasing Ag content and the stability of phase change film is improved greatly. Structures were measured by x-ray diffraction and the face-centered-cubic structure was more stable after Ag doping. Four-point probe was used to measure the sheet resistance of Agdoped Ge2Sb2 Te5 films annealed at different temperatures and it is indicated that Ag atoms increase the sheet resistance of Ge2Sb2 Te5 thin film when the annealing temperature is higher than about 360℃, which is beneficial for reducing the reset current. Current-voltage curves were tested and it is demonstrated that 4.5 at. % Ag doping into the Ge2Sb2Te5 film can reduce the threshold current from 1.46mA to 0.25mA and can only increase the threshold voltage slightly, which is very useful for low energy consumption.     

Bi-Sb-Te基热电薄膜温差电池离子束溅射制备与表征

本文采用离子束溅射Bi/Te和Sb/Te二元复合靶,直接制备n型Bi₂Te₃热电薄膜和p型Sb₂Te₃热电薄膜.在退火时间同为1 h的条件下,对所制备的Bi₂Te₃薄膜和Sb₂Te₃薄膜进行不同温度的退火处理,并对其热电性能进行表征.结果表明,在退火温度为150 ℃时,制备的n型Bi₂Te₃关键词： 薄膜温差电池 2Te₃薄膜')" href="#">Sb₂Te₃薄膜 2Te₃薄膜')" href="#">Bi₂Te₃薄膜 离子束溅射     

Characteristics of Sn-Doped Ge2Sb2Te5 Films Used for Phase-Change Memory

Sn-doped Ge2Sb2Te5 thin films deposited on Si（100）/SiO2 substrates by rf magnetron sputtering are investigated by a differential scanning calorimeter, x-ray diffraction and sheet resistance measurement. The crystallization temperatures of the 3.58 at.%, 6.92 at.% and 10.04 at.% Sn-doped Ge2Sb2Te5 thin films have decreases of 5.3, 6.1 and 0.9℃, respectively, which is beneficial to reduce the switching current for the amorphous-to-crystalline phase transition. Due to Sn-doping, the sheet resistance of crystalline Ge2Sb2Te5 thin films increases about 2-10 times, which may be useful to reduce the switching current for the amorphous-to-crystalline phase change. In addition, an obvious decreasing dispersibility for the sheet resistance of Sn-doped Ge2Sb2Te5 thin films in the crystalline state has been observed, which can play an important role in minimizing resistance difference for the phase-change memory cell element arrays.     

激光致晶态Ag11In12Te26Sb51相变介质光学常数的研究

研究了结晶度对Ag11In12 Te2 6Sb51相变薄膜光学常数的影响。用初始化仪使相变薄膜晶化 ,改变晶化参量得到不同的结晶度 ,当转速固定时 ,随激光功率的增加 ,折射率基本随之减小 ,消光系数先是增大 ,而后减小 ;当激光功率固定时 ,随转速的增大 ,折射率也随之增大 ,消光系数也是先增大后减小。非晶态与晶态间的变换、薄膜微结构的变化 (包括晶型的转变和原子间键合状态的变化 )以及薄膜内残余应力是影响Ag11In12 Te2 6Sb51相变薄膜复数折射率的主要原因。测量了单层膜的透过率和CD RW相变光盘中Ag11In12 Te2 6Sb51薄膜非晶态和晶态的反射率     

高压下稳态六方Ge2Sb2Te5结构、电子和光学性质的第一性原理研究

采用基于密度泛函理论的广义梯度近似方法研究了稳态六方petrov原子序列结构Ge2Sb2Te5的结构、电子和光学性质。计算所得的平衡态晶格参数与实验数据和先前的理论结果吻合很好。基态的能带结构和态密度表明了稳态六方petrov原子序列结构的Ge2Sb2Te5持有金属性。从压强影响下体积的变化趋势发现稳态六方Ge2Sb2Te5在17 GPa和34 GPa 出现不稳定,暗示在此压强下的相变发生,这与2009年Krbal等人的实验结果相吻合。同时,还系统地研究了稳态六方petrov原子序列结构的Ge2Sb2Te5高压下的光学性质,得到了高压下介电函数、吸收率、光反射率、折射率、消光系数和电子能量损失谱在20 eV内的变化情况。     

在预刻蚀的衬底上通过分子束外延直接生长出拓扑绝缘体薄膜的微器件

在利用光刻将拓扑绝缘体外延薄膜加工成微米尺寸结构的过程中,所用的各种化学物质会导致薄膜质量的下降.在实验中,通过在钛酸锶衬底上预先光刻出Hall bar形状的凸平台并以此为模板进行拓扑绝缘体(Bi x Sb1-x)2Te3薄膜的分子束外延生长,直接获得了薄膜的Hall bar微器件,从而避免了光刻过程对材料质量的影响.原子力显微镜和输运测量结果均显示该微器件保持了(Bi x Sb1-x)2Te3外延薄膜原有的性质.这种新的微器件制备方法有助于在拓扑绝缘体中实现各种新奇的量子效应,并可推广于其他外延生长的低维系统.     

Si3.5Sb2Te3 Phase Change Material for Low-Power Phase Change Memory Application

Novel Si3.5Sb2Te3 phase change material for phase change memory is prepared by sputtering of Si and Sb2Te3 alloy targets. Crystalline Si3.5Sb2Te3 is a stable composite material consisting of amorphous Si and crystalline Sb2Te3, without separated Te phase. The thermally stable Si3.5Sb2Te3 material has data retention ability （10 years at 412K） better than that of the Ge2Sb2Te5 material （10 years at 383 K）. Phase change memory device based on Si3.5Sb2Te3 is successfully fabricated, showing low power consumption. Up to 2.2 × 107 cycles of endurance have been achieved with a resistance ratio lager than 300.     

The engineering of doxorubicin-loaded liposome-quantum dot hybrids for cancer theranostics

In the fabrication of phase change random access memory(PRAM) devices, high temperature thermal processes are inevitable. We investigate the thermal stability of Ge2Sb2Te5(GST) which is a prototypical phase change material. After high temperature process, voids of phase change material exist at the interface between Ge2Sb2Te5 and substrate in the initial open memory cell. This lower region of Ge2Sb2Te5 is found to be a Te-rich phase change layer. Phase change memory devices are fabricated in different process conditions and examined by scanning electron microscopy and energy dispersive X-ray. It is found that hot-chuck process, nitrogen-doping process, and lower temperature inter-metal dielectric(IMD) deposition process can ease the thermal impact of line-GST PRAM cell.     

退火处理对W:Bi4Ge3O12和Bi12GeO20晶体发光性能的影响

通过提拉法制备了W:Bi4 Ge3 O12和Bi12GeO20晶体,测试了晶体的吸收光谱、光致发光谱和发光衰减时间等.W:Bi4 Ge3 O12的可见光发光强度比纯Bi4 Ge3 O12有所增强,而且N2中退火处理对W:Bi4Ge3O12发光有进一步增强作用.Bi12GeO20在N2中退火处理后在745 nm附近有发光...     

退火温度对a-Se0.70Ge0.15Sb0.15薄膜的结构和光学性质的影响

研究了退火温度对Se0.70Ge0.15Sb0.15薄膜的影响.通过热蒸发技术,在300K温度下将大块无定形Se0.70Ge0.15Sb0.1s沉积在石英和玻璃衬底上.研究发现,未经过退火处理的薄膜结构和在300K,1.33×10-5Pa下退火1小时后的薄膜结构都是无定形结构,而在同样气压470K温度下退火1小时的薄膜有结晶现象.通过在300 2 500nm范围内垂直入射光方向上透射率和反射率的测试,研究了薄膜的一些光学参数,如消光系数(k),折射系数(n)和吸收系数(a).研究发现,n和k同热处理温度有关.通过光学数据的分析,得到了不同条件下薄膜的间接带隙宽度(Enong),未经过热处理薄膜的Enong是1.715±0.021eV,300K下退火薄膜的Enong是1.643±0.021eV,470K下退火的Enong是1.527±0.021eV.退火温度降低了带隙宽度Enong,但增加了带尾eo这种效应可以根据Mott和Davis提出的多晶体系中态密度来解释.     

Sb_2Te_3热电薄膜的离子束溅射制备与表征

采用离子束溅射技术交替沉积Sb-Te-Sb多层薄膜后进行高真空热处理,直接制备Sb2Te3薄膜.利用X射线衍射(XRD)仪、霍尔系数测试仪、薄膜Seebeck系数测量系统对所制备的薄膜特性进行表征.XRD测量结果显示,薄膜的主要衍射峰与Sb2Te3标准衍射峰相同,在[101]/[012]晶向取向明显,存在较多的Te杂质峰;霍尔系数测试结果表明,薄膜为p型半导体薄膜,薄膜电阻率较低,其电导率接近于金属电导率,载流子浓度量级为1023cm-3,具有良好的电学性能;Seebeck系数测量结果显示,薄膜具有良好的热电性能,在不同条件下制备的薄膜的Seebeck系数在7.8—62μV/K范围;在所制备的薄膜中,退火时间为6h、退火温度为200℃的薄膜其Seebeck系数达到最大,约为62μV/K,且电阻率最小.     

激光致晶态Ag11In12Te26Sb51相变介质光学常量的研究

研究了结晶度对Ag11In12Te26Sb51相变薄膜光学常数的影响。用初始化仪使相变薄膜晶化，改变晶化参量得到不同的结晶度，当转速固定时，随激光功率的增加，折射率基本随之减小，消光系数先是增大，而后减小；当激光功率固定时，随转速的增大，折射率也随之增大，消光系数也是先增大后减小。非晶态与晶态间的变换、薄膜微结构的变化（包括晶型的转变和原子间键合状态的变化）以及薄膜内残余应力的影响Ag11In12Te26Sb51相变薄膜复数折射率的主要原因。测量了单层膜的透过率和CD－RW相变光盘中Ag11In12Te26Sb51薄膜非晶态和晶态的反射率。