硫系薄膜的力学及摩擦性能研究

利用电子回旋共振CVD设备制备了一种硫系GeSbTe薄膜,并用纳米硬度计考察了其抗压性能,同时采用划痕实验以及摩擦力显微镜研究了GeSbTe薄膜的摩擦特性.结果表明:GeSb2Te4膜的微观抗载荷性能随着膜厚的增加而显著增强;对于90nm厚度的GeSb2Te4来说,施加1000霳左右的载荷所获得的硬度和弹性模量值受基体的影响较小,分别为2.07GPa、38.70GPa;湿度对Ge2Sb2Te5膜和针尖粘附的影响没有GeSb2Te明显,而且粘附力的存在会改变摩擦系数.     

提高压电微探针表面信息读取电荷灵敏度的方法

分析了基于原子力显微镜（AFM）探针阵列的超高密度信息存储中压电方式读取纳米数据坑的电荷灵敏度,从探针结构设计的角度指出通过改连上电极钝化层的设计可以使电荷灵敏度提高约50％;在读取电路中引入直流偏置电压,通过提高锆钛酸铅（PZT）薄膜的等效横向压电系数d31进一步提高电荷灵敏度．利用硅片悬臂梁上溶胶-凝胶法制备的PZT薄膜,基于正压电效应实验验证了施加直流偏置电压对d31的提高作用．直流偏压从0V增加到10V时,等效横向压电系数d31从-48pC／N提高到-120pC／N．     

Sb-Se系和Ge-Sb-Te系粉末材料热力学参数测试

利用DSC对Sb Se系和Ge Sb Te系粉末热力学参数进行了研究 ,对于Sb Se系合金 ,仅在温度为 2 2 0℃左右时出现一个放热峰 ,而对于GeSb2 Te4 与GeSb4 Te4 合金 ,分别在 140℃及2 0 0℃左右各出现一个放热峰 ,加热速度不同放热峰出现温度略有差别     

基于Sn掺杂Ge2Sb2Te5的相变存储器器件单元存储性能

采用0.18μm标准工艺制备出基于Sn掺杂Ge2Sb2Te5相变材料的相变存储器器件单元,利用自行设计搭建的电学测试系统研究了其存储性能.结果表明:Sn的掺杂没有改变Ge2Sb2Te5的相变特性,其相变阚值电压和阈值电流分别为1.6V和25μA;实现了器件单元的非晶态(高阻)与晶态(低阻)之间的可逆相变过程;器件单元中相变材料结晶所需电流最低为1.78mA(电流宽度固定为100ns)、结晶时间大于80ns(电流高度固定为3mA);相变材料非晶化脉冲电流宽度为30ns时,所需电流大于3.3mA;与Ge2Sb2Te5相比,Sn的掺杂降低了SET操作的脉冲电流宽度,提高了结晶速度,有利于提高相变存储器的存储速度.     

基于Ga-SbTe的高性能相变存储单元的设计和仿真

相变存储器(PCM)因依靠电阻率的变化来存储的模式,成为65nm以下非易失存储器应用的研究热点.然而,相变存储器的擦写功耗、复位电压、热稳定性和擦写寿命一直是相变存储器发展的几个瓶颈.对此,设计了一种基于相变合金Ga3Sb8Te1的新型嵌入式相变存储器,并建立有限元(FEA)热学,结晶动力学和SPICE宏模型.通过瞬态热学和结晶动力学仿真表明,基于Ga3sb8Te1的相变存储器具有更高的热稳定性和可循环擦写次数、更低的复位功耗,更快的置位频率,是一种较为理想的高性能相变存储器.     

Sb—Se系和Ge—Sb—Te系粉末材料热力学参数测试

利用DSC对Sb-Se系和Ge-Sb-Te系粉末热力学参数进行了研究，对于Sb-Se系合金，仅在温度为220℃左右时出现一个放热峰，而对于GeSb2tE4与GeSb4Te4合金，分别在140℃及200℃左右出现一个放热峰，加热速度不同放热峰出现温度略有差别。     

AFM动态电场诱导氧化加工的电流分析

对Si表面动态电场作用下利用原子力显微镜(atomic force microscope,AFM)诱导氧化加工进行了实验研究,通过监测加工过程中的电流变化进行了加工机理和工艺的分析.施加的动态电场为方波,频率范围为1 Hz～10MHz,获得的氧化物高度为1 nm～2 nm.实验结果表明氧化加工过程中,探针、氧化物和Si之间构成了导体-绝缘体-半导体隧道结,其电容效应会影响氧化物的继续生成.采用调制电压进行诱导氧化加工可以提高氧化物的生长速度和优化氧化物的纵横比.实验得出采用频率约为10～100 Hz的调制电压,可获得最优的纵横比.     

基于导电AFM类金刚石膜表面改性研究

用导电原子力显微镜(AFM)针对宏观上绝缘,微观上由导电相sp2和绝缘相sp3混合的类金刚石(DLC)膜,进行表面改性的研究,尤其观察DLC膜表面施加电压前后形貌变化。实验表明,当直流电压加在针尖上,DLC膜形貌未发生变化,而电压施加在样品表面则出现明显纳米加工凹坑。解释了凹坑的“蝴蝶坑”形成原因;对DLC膜力电耦合实验表明,在一定临界压力之下,随针尖对样品作用力的加大,凹坑的深度随之增加。     

碲基复合薄膜在纳米尺度下的电学特性研究

分别采用AFM和原子力/扫描探针显微镜(AFM/SPM)在纳米尺度下对碲基复合(Te/TeO2-SiO2)薄膜的表面电势、电容梯度等电学特性进行测量。测试结果表明控制电压为-0.8V,反应时间为200s条件下制备的碲基复合薄膜的表面电势差达到700mV,相对介电常数小于以硅为主要成分的衬底相对介电常数。利用光谱分析,碲基复合薄膜的禁带宽度约为3.14eV。     

等离子体化学的气相沉积金刚石膜过程中光发射谱和朗谬尔探针原位诊断

报道了利用光发射谱（OES）和朗谬尔探针对热阴极直流放电等离子体化学气相沉积金刚石薄膜的等离子体条件进行原位研究的部分结果,研究了几种过程参数变化中等离子体状态,并与金刚石膜的沉积相联系。当CH4浓度变化时,CH基团的发射强度和电子密度ne的变化表现出相似趋势,均出现一极大值。而在高CH4浓度,C2的发射出现。在气压变化过程中,CH的发射强度和ne均随气压的升高而下降,C2的发射强度变化不大。用OES和朗谬尔探针测量的电子温度Te所显示的结果是一致的。在这些过程中,电子碰撞应该是CH发射的主要机制,C2的发射应该来源于化学发光或热激发。     

Minimum voltage for threshold switching in nanoscale phase-change memory

The size scaling of the threshold voltage required for the amorphous-to-crystalline transition in phase-change memory (PCM) is investigated using planar devices incorporating individual GeTe and Sb2Te3 nanowires. We show that the scaling law governing threshold switching changes from constant field to constant voltage scaling as the amorphous domain length falls below 10 nm. This crossover is a consequence of the energetic requirement for carrier multiplication through inelastic scattering processes and indicates that the size of PCM bits can be miniaturized to the true nanometer scale.     

Finite-element model for phase-change recording

The finite-element method is applied to model phase-change recording in a grooved recording stack. A rigorous model for the scattering of a three-dimensional focused spot by a one-dimensional periodic grating is used to determine the absorbed light in a three-dimensional region inside the phase-change layer. The optical model is combined with a three-dimensional thermal model to compute the temperature distribution. Land and groove recording and polarization dependence are studied, and the model is applied to the Blu-ray Disc.     

Ultra-high-density phase-change storage and memory

Phase-change storage is widely used in optical information technologies (DVD, CD-ROM and so on), and recently it has also been considered for non-volatile memory applications. This work reports advances in thermal data recording of phase-change materials. Specifically, we show erasable thermal phase-change recording at a storage density of 3.3 Tb inch(-2), which is three orders of magnitude denser than that currently achievable with commercial optical storage technologies. We demonstrate the concept of a thin-film nanoheater to realize ultra-small heat spots with dimensions of less than 50 nm. Finally, we show in a proof-of-concept demonstration that an individual thin-film heater can write, erase and read the phase of these storage materials at competitive speeds. This work provides important stepping stones for a very-high-density storage or memory technology based on phase-change materials.     

Measurement of the thermal coefficients of rewritable phase-change optical recording media

We describe a method to estimate the heat capacity of the substrate, the dielectric layer, and the phase-change layer of phase-change optical recording media as well as the thermal conductivity of the phase-change layer in its crystalline state. Measurements were carried out on spinning disks with the beam of light focused and locked onto the groove track. The method relies on the identification of the solid-to-liquid phase transition that occurs in the phase-change layer and takes advantage of the dependence of thermal diffusion on track velocity and irradiation time.     

Multispeed rewritable optical-recording method with an initialization-free phase-change disk

A new method of multispeed rewritable optical recording is presented. An initialization-free phase-change optical disk is proposed as a candidate for multispeed rewritable optical recording. The simulated results of the initialization-free disk at different linear velocities show that the cooling rate increases from approximately 18.69% to 37.96%. A model that combines the crystallization acceleration effect due to the additional layers and the rapid cooling rate due to the initialization-free disk structure is proposed as the physical mechanism of the multispeed recording method with an initialization-free disk. The dynamic optical-recording properties of the initialization-free DVD-RAM disk at different recording speeds shows that the initialization-free phase-change optical-recording disk is compatible with a broad range of recording speeds from 3.49 to 12.21 m/s.     

利用原子力显微镜改变P(VDF/TrFE)聚合物分子链偶极子极性实现数据存储的读/写/擦除/改写

包括读、写、擦除和改写等信息存储现象的产生是由于在外加电压的作用下，铁电体“聚偏二氟乙烯-三氟胸苷”异分子聚合物的分子链偶极子的极性发生了变化．为达此目的，使原子力显微镜工作在压电响应模式下，它比传统的数据存储方法要有优势．将20nm厚的“聚偏二氟乙烯-三氟胸苷”薄膜放置于原子力显微镜的导电悬臂梁触针和石墨基片之间，直流电通过AFM触针在几微秒的时间内极化铁电畴，同时用交流电来辨识这些纳米尺度(约60nm)的铁电畴，这些铁电畴的尺寸由外加电压的大小和持续时间等参数来决定，可以实现约19．2Gb／cm^2(120Gb／in^2)的数据存储．     

Mirror hologram recording with a phase-change medium

We propose mirror hologram recording with a phase-change material, which has a large refractive-index difference between its amorphous and crystalline states. It offers excellent diffraction efficiency and is erasable and nonvolatile. We designed an optimum multilayer structure for high diffraction efficiency by simulating the effect of each film thickness on diffraction efficiency. Experiments with a germanium tellurium alloy as the phase-change material show a high diffraction efficiency close to the calculated value. This medium can also be used for directly drawing computer-generated holograms. Lee-type computer-generated holograms were drawn on this medium with optical-disk technology.