原子层沉积超薄氮化铝薄膜的椭圆偏振光谱法表征

采用原子层沉积(ALD)工艺在硅衬底上生长了35 nm以下不同厚度的超薄氮化铝(AlN)晶态薄膜。利用椭圆偏振光谱法在波长275~900 nm内测量并拟合薄膜的厚度及折射率和消光系数等光学参数。利用原子力显微镜(AFM)表征AlN晶粒尺寸随生长循环次数的变化,计算得到薄膜表面粗糙度并用于辅助椭偏模型拟合。针对ALD工艺特点建立合适的椭偏模型,可获得AlN超薄膜的生长速率为0.0535 nm/cycle,AlN超薄膜的折射率随着生长循环次数的增加而增大,并逐渐趋于稳定,薄膜厚度为6.88 nm时,其折射率为1.6535,薄膜厚度为33.01 nm时,其折射率为1.8731。该模型为超薄介质薄膜提供了稳定、可靠的椭圆偏振光谱法表征。     

基于ZnO-CuO纳米线结构的新型光电器件

为了获得高效的整流器件和微型短波长的发光器 件,采用原子层沉积(ALD)法和水浴法合成了具有 ZnO-CuO的结构器件。对制备的样品进行了光学和电学特性的检测,获得了22.79的整流比和17.69的理想 因子,且门限电压和整流比等特性随CuO厚度增加而减小。在光致发光(PL)特性上,具有 显著的由ZnO带电激发的385nm紫外光波峰,同时伴有由深能级散射 激发的572nm的可见光波峰,且随着CuO厚度的增加紫外光波峰减小 ,可见光峰变大。实验结果表明,本文制备的器件可以应用在纳米型二极管、光电探测器以 及微型光源等领域。     

原子层沉积氧化物包覆层对奥克托金感度的影响

通过原子层沉积(ALD)技术在微米级奥克托今(HMX)炸药颗粒表面包覆了氧化铝和氧化锌薄膜.采用X射线光电子能谱和扫描电子显微镜对包覆后HMX颗粒的表面化学组成和形貌进行了表征,利用差示扫描量热法和热重法分析了包覆后HMX的热分解行为.测试了ALD氧化物包覆的HMX的机械感度和静电火花感度,研究了HMX颗粒表面包覆层的组成和厚度对其感度的影响.结果表明,ALD氧化铝或氧化锌薄膜均能够完整、均匀地覆盖HMX颗粒的全部外表面,薄膜厚度在纳米尺度范围内精确可调.ALD氧化铝或氧化锌薄膜对HMX的热分解性能影响很小.由于金属氧化物具有很高的硬度,ALD氧化铝或氧化锌包覆膜不能降低HMX的机械感度.但氧化物薄膜具有一定的导电性,可降低HMX的静电火花感度.     

有机电致发光器件的新型薄膜封装技术研究

针对有机电致发光器件(OLED)在空气中水汽和O2作用下寿命下降的问题,提出一种对OLED进行薄膜封装方法。封装薄膜由电子束蒸镀Al2O3薄膜和原子层沉积(ALD,atomic layer deposition)Al2O3薄膜相结合形成。利用Ca薄膜电学测试方法测定封装薄膜的水汽透过率(WVTR)。具体实现方法是,采用玻璃作为衬底,在100nm的Al电极上蒸镀200nm的Ca膜,然后对整个系统进行薄膜封装,只留出Al电极的一部分作为探针接触电极。实验发现,采用电子束蒸镀结合ALD的Al2O3薄膜封装,Ca薄膜变成透明的时间比未封装或采用单一结构封装得到了延长。为了检验薄膜封装效果,制作了一组绿光OLED,器件结构为ITO/MoOX(5nm)/mMTDATA(20nm)/NPB(30nm)/Alq3(50nm)/LiF(1nm)/Al,实验结果表明,本文提出的薄膜封装方法对器件进行封装,器件的寿命得到了延长。     

X-ray metrology for high-k atomic layer deposited HfxZr1−xO2 films

Hafnium-based dielectrics are the most promising material for SiO₂ replacement in future nodes of CMOS technology. While devices that utilize HfO₂ gate dielectrics suffer from lower carrier mobility and degraded reliability, our group has recently reported improved device characteristics with a modified Hf_xZr_1−xO₂ [R.I. Hegde, D.H. Triyoso, P.J. Tobin, S. Kalpat, M.E. Ramon, H.-H. Tseng, J.K. Schaeffer, E. Luckowski, W.J. Taylor, C.C. Capasso, D.C. Gilmer, M. Moosa, A. Haggag, M. Raymond, D. Roan, J. Nguyen, L.B. La, E. Hebert, R. Cotton, X.-D. Wang, S. Zollner, R. Gregory, D. Werho, R.S. Rai, L. Fonseca, M. Stoker, C. Tracy, B.W. Chan, Y.H. Chiu, B.E. White, Jr., in: Technical Digest - International Electron Devices Meet, vol. 39, 2005, D.H. Triyoso, R.I. Hegde, J.K. Schaeffer, D. Roan, P.J. Tobin, S.B. Samavedam, B.E. White, Jr., R. Gregory, X.-D. Wang, Appl. Phys. Lett. 88 (2006) 222901]. These results have lead to evaluation of X-ray reflectivity (XRR) for monitoring high-k film thickness and control of Zr addition to HfO₂ using measured film density. In addition, a combination of XRR and spectroscopic ellipsometry (SE) is shown to be a fast and non-intrusive method to monitor thickness of interfacial layer between high-k and the Si substrate.     

Characterization of Cd1-xZnxTe (0≤x≤1) Nanolayers Grown by Atomic Layer Deposition on GaSb and GaAs (001) Oriented Substrates

ZnTe, CdTe, and the ternary alloy CdZnTe are important semiconductor materials used widely for the detection of an important range of electromagnetic radiation as gamma ray and X-ray. Although, recently these materials have acquired renewed importance due to the new explored nanolayer properties of modern devices. In addition, as shown in this work they can be grown using uncomplicated synthesis techniques based on the deposition in vapour phase of the elemental precursors. This work presents the results obtained from the deposition of nanolayers of these materials using the precursor vapour on GaAs and GaSb (001) substrates. This growth technique, extensively known as atomic layer deposition (ALD), allows the layers growth with nanometric dimension. The main results presented in this work are the used growth parameters and the results of the structural characterization of the layers by the means of Raman spectroscopy measurements. Raman scattering shows the peak corresponding to longitudinal optical (LO)-ZnTe, which is weak and slightly redshift in comparison with that reported for the ZnTe bulk at 210 cm–1. For the case of the CdTe nanolayer, Raman spectra presented the LO-CdTe peak, which is indicative of the successful growth of the layer. Its weak and slightly redshift in comparison with that reported for the CdTe bulk can be related with the nanometric characteristic of this layer. The performed high-resolution X-ray diffraction (HR-XRD) measurement allows to study some important characteristics such as the crystallinity of the grown layer. In addition, the HR-XRD measurement suggests that the crystalline quality has dependence on the growth temperature.     

N_2和NH_3退火对铪铝氧栅介质C-V特性的影响

采用原子层淀积(ALD)的方法在Si(100)衬底上制备了铪铝氧(HfAlO)高介电常数介质,并研究了N2和NH3退火对于介质薄膜的影响。改变原子层淀积的工艺,制备了三组含有不同Al∶Hf原子比的铪铝氧(HfAlO)高介电常数介质。电容电压特性(C-V)测试表明,薄膜的积累电容密度随着薄膜中Al∶Hf原子比的减少而增加。实验表明,用N2和NH3对样品进行淀积后退火,可以减小等效电容厚度(CET)、降低固定正电荷密度以及减小滞回电压,从而有效地提高了介质薄膜的电学特性。     

Improved electrical behavior of ZrO2-based MIM structures by optimizing the O3 oxidation pulse time

The influence of oxidation pulse during atomic layer deposition (ALD) process on electrical and dielectric properties of metal–insulator–metal (MIM) structures with different ZrO₂-based (e.g. pure ZrO₂, Al- and Si- doped ZrO₂) high-k dielectrics and different thicknesses has been investigated. Strongly pulse-time dependent as well as independent phenomena are observed and their thorough analysis has given more insight on the processes taking place in these structures thus allowing further optimization of their electrical performance. Longer oxidation pulses produce films with larger thicknesses which may be related to the incorporation of excess oxygen in the layers and the formation of less dense films. Incorporation of Al and 10 s pulse time are the most beneficial and provide structures with the lowest leakage current. At high positive voltages a significant increase of current and a change of I–V curve shape with increasing pulse time have been observed. The possible processes which provoke this change have been discussed. The analysis of leakage current mechanisms reveals that neither incorporation of Al or Si in ZrO₂ nor oxidation pulse time change the energy position of traps participating in the conduction process, hence the nature of these traps remains unaffected – it is a single positively charged oxygen vacancy in ZrO₂. The oxidation pulse time of 5–10 s is the optimal one which provides structures fulfilling the requirements for next generation MIM-based dynamic random access memories (DRAMs).     

Influence of the surface roughness of the bottom electrode on the resistive-switching characteristics of Al/Al2O3/Al and Al/Al2O3/W structures fabricated on glass at 300 °C

Resistive-switching devices based on Metal–Insulator–Metal (MIM) structures have shown promising memory performance characteristics while enabling higher density of integration. Usually, these MIM devices are fabricated using different processing conditions including high temperature thermal treatments that could lead to undesirable chemical reactions in the insulator material and at its interface with the metals involved. In this work, we compare the electrical characteristics of MIM devices (fabricated on glass at 300 °C) that use aluminum or tungsten as bottom electrode (BE) in order to study the influence of a highly reactive (aluminum) or inert (tungsten) metal electrode on the memory characteristics. We found that the switching characteristics of Al₂O₃ (from a high-resistance state HRS to a low-resistance state LRS and vice versa), are highly dependent on the surface roughness of the BE, the thickness of Al₂O₃ and the current compliance (CC) which limits the electron density flowing through both top/bottom electrodes.     

Dual-Shelled RbLi(Li3SiO4)2:Eu2+@Al2O3@ODTMS Phosphor as a Stable Green Emitter for High-Power LED Backlights

The stability of luminescent materials is a key factor for the practical application in white light-emitting diodes (LEDs). Poor chemical stability of narrow-band green-emitting RbLi(Li₃SiO₄)₂:Eu²⁺ (RLSO:Eu²⁺) phosphor hinders their further commercialization even if they have excellent stability against thermal quenching. Herein, we propose an efficient protection scheme by combining the surface coating of amorphous Al₂O₃ and hydrophobic modification by octadecyltrimethoxysilane (ODTMS) to construct the moisture-resistant dual-shelled RLSO:Eu²⁺@Al₂O₃@ODTMS composite. The growth mechanisms of both the Al₂O₃ inorganic layer and the silane organic layer on the phosphor surface are investigated. The results remarkably improve the water-stability of this narrow-band green emitter. The evaluation of the white LED by employing this composite as the green component demonstrates that RLSO:Eu²⁺@Al₂O₃@ODTMS is a promising candidate for the high-performance display backlights, and this dual-shelled strategy provides an alternative method to improve the moisture-resistant property of humidity-sensitive phosphors.