MOCVD生长中载气H2对N掺杂ZnO性质的影响

采用MOCVD方法在石英衬底上生长ZnO。实验使用二乙基锌(DEZn)为锌源,N2O作为氧和氮源,H2作为载气。采用PL和Raman光谱方法对ZnO样品进行表征,结果表明H2的加入大幅度减少薄膜中碳的掺入,明显改善了薄膜的光学质量。采用N2O离化技术,可以进一步提高其带边峰的强度,抑制带内发光。XRD测量表明,生长的ZnO薄膜具有c轴择优取向。目前生长高质量N掺杂的p型ZnO薄膜是很困难的,而H2作为载气的加入明显改善了ZnO薄膜的光学性质,在生长过程中加入H2将为获得高质量N掺杂的p型ZnO薄膜提供一种途径。     

常压化学气相沉积技术生长ZnO:H薄膜的光学性质

采用常压金属有机物化学气相沉积技术(AP-MOCVD),以二乙基锌(DEZn)为Zn源,去离子水(H2O)为氧源,N2作载气,在外延ZnO薄膜的反应气氛中通入少量氢气,在c-Al2O3衬底上生长出了ZnO∶H薄膜。用X射线双晶衍射和光致发光谱对ZnO∶H薄膜的结晶性能和光学性质进行表征。结果表明,ZnO∶H薄膜(002)和(102)面的Ω扫描半峰全宽分别为46.1 mrad和81.4 mrad,表明该薄膜具有良好的结晶性能;室温下,ZnO∶H薄膜具有较强的紫外光发射(380 nm),在低温10 K光致发光谱中观测到位于3.3630 eV处与氢相关的中性施主束缚激子峰(I4)及其位于3.331 eV处的双电子卫星峰(TES)。采用退火的方法,通过观测I4峰的强度变化,研究了氢在ZnO∶H薄膜中的热稳定性。发现随着退火温度的升高,I4峰的强度逐渐减弱,表明在高温下退火,氢会从ZnO薄膜中逸出。     

N2O为氧源金属有机化学气相沉积生长ZnO薄膜的光学性能研究

采用常压金属有机化学气相沉积(AP-MOCVD)技术、三步生长法,分别以H2O和N2O为氧源,DEZn为Zn源,N2作载气,在c-Al2O3衬底上生长出了晶体质量较好的ZnO薄膜。用X射线双晶衍射(DCXRD)和光致发光谱对ZnO薄膜的结晶性能和光学性质进行表征。结果显示,ZnO倾斜对称面(10-12)的ω扫描半峰全宽为350″,表明ZnO薄膜结晶性能良好;低温10 K光致发光谱结果表明,N2O为氧源生长的ZnO膜和H2O为氧源生长的ZnO膜的发光特性明显不同,没有观察到与氢有关的中性施主束缚激子对应的3.331 eV双电子卫星峰(TES)。这一结果表明,用N2O为氧源生长的ZnO薄膜中不易引进氢杂质。     

常压化学气相沉积技术生长ZnO∶H薄膜的光学性质

采用常压金属有机物化学气相沉积技术(APMOCVD),以二乙基锌(DEZn)为Zn源,去离子水(H2O)为氧源,N2作载气,在外延ZnO薄膜的反应气氛中通入少量氢气,在cAl2O3衬底上生长出了ZnO∶H薄膜。用X射线双晶衍射和光致发光谱对ZnO∶H薄膜的结晶性能和光学性质进行表征。结果表明,ZnO∶H薄膜(002)和(102)面的Ω扫描半峰全宽分别为46.1 mrad和81.4 mrad,表明该薄膜具有良好的结晶性能；室温下,ZnO∶H薄膜具有较强的紫外光发射(380 nm),在低温10 K光致发光谱中观测到位于3.3630 eV处与氢相关的中性施主束缚激子峰(I4)及其位于3.331 eV处的双电子卫星峰(TES)。采用退火的方法,通过观测I4峰的强度变化,研究了氢在ZnO∶H薄膜中的热稳定性。发现随着退火温度的升高,I4峰的强度逐渐减弱,表明在高温下退火,氢会从ZnO薄膜中逸出。     

溶胶-凝胶旋涂法制备In-N共掺ZnO薄膜及其光学性能研究

ZnO是目前使用广泛的半导体材料,但本征ZnO存着在一定的缺陷,现通过溶胶-凝胶旋涂法分别以乙酸锌(Zn(CH3 COO)2?2H2 O)为锌源、硝酸铟(In(NO3)3?H2 O)为铟源、氯化铵(NH4 Cl)为氮源制备了In-N共掺的ZnO薄膜,由此来改善其相关性能.所制备样品的晶格结构、表面形貌、光学透过率及光学...     

纳米硅薄膜的生长动力学与计算机模拟

氢化纳米硅(nc-Si:H)薄膜由于其具有奇异的结构和独特的性质,而引起广泛的关注.本文在等离子体增强化学气相淀积(PECVD)系统中,以高纯H₂高度稀释SiH₄为反应气体源,在射频和直流双重功率源的激励下制备成功具有纳米结构的nc-Si:H薄膜.利用高分辨率电子显微镜(HREM)、Raman散射谱(RSS)、扫描隧道电子显微镜(STM)等实验技术对nc-Si:H薄膜样品作了研究.基于对薄膜制备过程的动力学分析,提出nc-Si:H薄膜的分形生长模型:扩散与反应限 关键词：     

ZnO·TiO2双层复合薄膜的制备及其光学性能的研究

采用溶胶-凝胶法(Sol-Gel),分别以乙酸锌(Zn(CH₃COO)₂H₂O)、钛酸酊酯(Ti(OC₄H₉)₄)为锌源和钛源,在玻璃衬底以及硅衬底上制备了不同浓度的、均匀的、结晶质量良好的单层ZnO、TiO₂薄膜及双层的ZnO·TiO₂复合薄膜。结果表明,所制备的单层本征ZnO、TiO₂薄膜分别沿(002)、(101)晶面生长,且当本征ZnO、TiO₂的浓度分别为0.45 mol/L、0.65 mol/L时,择优取向生长最明显。ZnO·TiO₂复合薄膜的(101)、(004)特征峰明显,且0.45 mol/L/0.55 mol/L的双层ZnO·TiO₂复合薄膜结晶质量最好;薄膜表面最为平整,粒子分布均匀,粘连现象最少;对紫外光的吸收最强,禁带宽度为3.39 eV。     

MOCVD法生长ZnO薄膜时氧源 t-BuOH和H2O的比较研究

以活性较低的叔丁醇(t-BuOH)和水(H₂O)作为氧源,采用MOCVD技术生长了ZnO薄膜。研究发现,t-BuOH作为氧源可以有效地抑制其与锌源之间的气相预反应,比H₂O作为氧源进行ZnO薄膜的外延生长具有更高的生长速率,得到的ZnO薄膜晶体质量更优,同时载流子的迁移率可以达到37.0 cm²·V^-1·s^-1, 表明t-BuOH更适合作为氧源通过MOCVD系统生长ZnO薄膜。     

SiO2薄膜的液相沉积及特性

将基片浸入到低温SiO2过饱和的六氟硅酸（H2SiF6)溶液中,在其表面上沉积SiO2薄膜,这种新的生长工艺称之为液相沉积（LPD）。本文着重介绍LPD工艺及LPDSiO2薄膜的特性。     

用SiCl4/H2气源沉积多晶硅薄膜光照稳定性的研究

对以SiH4/H2及SiCl4/H2为源气体、采用等离子体增强化学气相沉积技术制备的非晶硅薄膜和多晶硅薄膜进行了光照稳定性的研究.实验表明,制备的多晶硅薄膜并没有出现非晶硅中的光致衰减现象,其光电导、暗电导在光照过程中没有下降反而有所上升且电导率变化快慢受氢稀释度的制约.多晶硅薄膜的光照稳定性可能来源于高的晶化度及Cl元素的存在.     

用锌金属有机源和二氧化碳等离子体增强化学气相沉积的方法制备高质量氧化锌薄膜

报道了用金属锌有机源和二氧化碳混合气源等离子体增强化学气相沉积(PECVD)的方法成功地制备高质量择优取向(0002)的ZnO薄膜。通过X-ray衍射谱进行了结构分析得到六方结构,择优取向,晶粒尺寸大约在220nn.并通过原子力显微镜分析更进一步验证了晶粒的尺寸。通过透射谱分析观察到了典型的激子吸收线。这种方法的特点是可以在低温条件下在任何衬底上生长大面积均匀性好、结晶度高的ZnO薄膜。     

ZnO薄膜的分子束外延生长及性能

利用分子束外延(MBE)和氧等离子体源辅助MBE方法分别在Si(100)、GaAs(100)和蓝宝石Al2O3(0001)衬底上用Zn、ZnS或以一定Zn-O化学计量比作缓冲层,改变衬底生长温度和氧压,并在氧气氛下,进行原位退火处理,得到ZnO薄膜。依据X射线衍射(XRD)图,表明样品的结晶性能尚好,且呈c轴择优取向;实验结果表明在不同衬底上生长的ZnO薄膜,由于晶格失配度不同,其衍射峰也有区别。用原子力显微镜(AFM)观测薄膜的表面形貌,为晶粒尺寸约几十纳米的ZnO纳米晶,且ZnO晶粒呈六边形柱状垂直于衬底的表面。采用掠入射X射线反射率法测膜厚。在360nm激发下,样品的发光光谱是峰值为410,510nm的双峰谱,是与样品表面氧缺陷有关的深能级发光。     

LiGaO2衬底上ZnO外延膜的结构与光学特性

采用磁控溅射法在(001),(100)及(010)LiGaO2衬底上制备了ZnO薄膜,通过X射线衍射(XRD)、原子力显微镜(AFM)、透过光谱以及光致发光谱(PL)对薄膜的结构、形貌及光学性质进行了表征.结果表明LiGaO2衬底不同晶面上制备的ZnO薄膜具有不同的择优取向,在(001)、(100)及(010)LiGaO2上分别获得了[001]、[1100]及[1120]取向的ZnO薄膜;不同取向的ZnO薄膜表面形貌差异较大;薄膜在可见光波段具有较高的透过率;在ZnO薄膜的光致发光谱中只观察到了位于378 nm的紫外发射峰,而深能级发射几乎观察不到,(1100)取向的薄膜紫外发射峰强度最大,半高宽也最小,薄膜光致发光件质的差异丰要和晶粒尺寸有关.     

溶胶-凝胶法制备氧化锌薄膜的压电行为

"采用溶胶-凝胶技术在单晶硅Si(111)上制备了ZnO压电薄膜,并以扫描电镜、X射线衍射仪(XRD)和原子力显微镜(AFM)进行了表征．XRD衍射实验表明ZnO薄膜随着膜厚的增大,其(002)取向逐渐增强;AFM研究了薄膜的表面形貌、粗糙度与晶粒大小的结果表明,ZnO压电薄膜的粗糙度与晶粒寸随着薄膜厚度的增大而减小．粗糙度为2.188~0.914 nm．利用PFM研究压电系数,发现随着薄膜厚度的增加,(002)生长方向增强,压电系数逐渐增大;当力参数小于薄膜的表面粗糙度时,压电系数测量不准确且在较大幅度     

Properties of ZnO thin films deposited by DC reactive magnetron sputtering under different plasma power

ZnO thin films were prepared by DC reactive magnetron sputtering under various values of the plasma power at room temperature. The samples were characterized with X-ray diffraction (XRD), optical transmittance, photoluminescence (PL), and atomic force microscopy (AFM), respectively. The results show that samples change from ZnO (110) dominant crystal orientation to ZnO (002) dominant crystal orientation with the increase of plasma power. The samples also exhibit compressive intrinsic stresses. The coherent domain size of the film crystallite along with the root mean square (RMS) of the surface roughness increases with the increase of the plasma power. Optical transmittance spectra reveal that all samples have excellent optical properties. With the increase of plasma power, slight optical transmittance decreasing and fundamental absorption edge red shifting were observed. Films prepared under higher plasma powers show weaker emission intensities, which may be related to substoichiometric composition.     

Temperature dependence of the optical band gap and electrical conductivity of sol-gel derived undoped and Li-doped ZnO films

Undoped and lithium (Li)-doped ZnO films were prepared by sol-gel method using spin coating technique. The effects of Li content on the crystallinity and morphological properties of ZnO films were assessed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). XRD patterns of the films showed the hexagonal wurtzite type polycrystalline structure and that the incorporation of lithium leads to substantial changes in the structural characteristics of ZnO films. The SEM and AFM measurements showed that the surface morphology of the films was affected from the lithium incorporation. The wrinkle network was observed on the surface from both SEM and AFM results for undoped ZnO. The wrinkle structure disappeared with increasing Li content. The absorption spectra of the ZnO and 5% Li-doped ZnO (LZO5) films were carried out between 140 and 400 K temperatures. The optical band gap of ZnO and LZO5 films (calculated at various temperatures) showed a linear dependence on the temperature. The absolute zero value optical band gap and the rate of change of the band gap with temperature of the ZnO and LZO5 films were found to be 3.339 and 3.322 eV, and 2.95 × 10⁻⁴ and 1.60 × 10⁻⁴ eV/K, respectively. The transport mechanisms in the ZnO and LZO5 films have been investigated by analyzing of the temperature (80-300 K) dependence of the conductivity. The activation energies of the ZnO film increased with Li content.     

Effects of oxygen pressures on pulsed laser deposition of ZnO films

Zinc oxide (ZnO) thin films on Si (1 1 1) substrates were deposited by pulsed laser ablation of ZnO target at different oxygen pressures. A pulsed Nd:YAG laser with wavelength of 1064 nm was used as laser source. The deposited thin films have been characterized by X-ray diffraction (XRD), Atomic force microscopy (AFM), and Raman spectroscopy. XRD measurements indicate that the ZnO thin films deposited at the oxygen pressure of 1.3 Pa have the best crystalline quality. AFM results show that the surface roughness of ZnO film increases with the increase of oxygen pressure. The Raman results indicate that oxygen ambient plays an important role in removing defects due to excess zinc.     

Thickness influence on surface morphology and ozone sensing properties of nanostructured ZnO transparent thin films grown by PLD

Transparent zinc oxide (ZnO) thin films with a thickness from 10 to 200 nm were prepared by the PLD technique onto silicon and Corning glass substrates at 350 °C, using an Excimer Laser XeCl (308 nm). Surface investigations carried out by atomic force microscopy (AFM) and X-ray diffraction (XRD) revealed a strong influence of thickness on film surface topography. Film roughness (RMS), grain shape and dimensions correlate with film thickness. For the 200 nm thick film, the RMS shows a maximum (13.9 nm) due to the presence of hexagonal shaped nanorods on the surface. XRD measurements proved that the films grown by PLD are c-axis textured. It was demonstrated that the gas sensing characteristics of ZnO films are strongly influenced and may be enhanced significantly by the control of film deposition parameters and surface characteristics, i.e. thickness and RMS, grain shape and dimension.     

Effect of ZnO doping on the structural and optical properties of BaWO<Subscript>4</Subscript> thin films prepared using pulsed laser ablation technique

BaWO₄ doped with ZnO (2, 3, 5, 7 and 10 wt%) nanostructured films are prepared on quartz substrates by pulsed laser ablation. The films are post annealed at 900°C. GIXRD analysis of the post-annealed films reveal the change of orientation of scheelite tetragonal crystal growth from 1 1 2 reflection plane to 0 0 4 planes when doping concentration is more than 3 wt%. The AFM images show that film with 7 wt% ZnO doping concentration has good ceramic pattern with surface features giving a minimum value of rms surface roughness suitable for optoelectronic device applications. The optical transmittance and band-gap energy of the films are found to decrease considerably on postannealing which can be due to the increase in grain size of the crystallites on annealing. Thus doping with ZnO improves the surface features of the films and increases the optical band-gap energy.     

p-type ZnO thin films grown by RF plasma beam assisted Pulsed Laser Deposition

The high exciton binding energy and band gap energy of ZnO thin films open the prospect of fabricating semiconductor lasers in the ultraviolet spectral range. A prerequisite for laser diode fabrication is highly p-doped ZnO which was not reproducibly obtained up to now. Without intentional doping ZnO exhibits n-type conduction. ZnO thin films have been obtained by radio-frequency assisted pulsed laser deposition. A metallic Zn target was used for ablation in an oxygen and nitrogen RF discharge. The electrical and morphological properties of the films grown on Si were studied by Atomic Force Microscopy (AFM), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), optical absorption and Hall Effect measurements for different ratios between the nitrogen and oxygen content. The AFM images of the as-grown ZnO films reveal high quality surfaces with low values for the surface roughness and a sharp distribution of grains sizes as an effect of the RF discharge. The XRD patterns for all samples exhibit only (002) and (004) peaks indicating that the c-axis is always oriented normal to the substrate surface. The films present p-type conductivity with different carrier concentration and mobility depending on the nitrogen/oxygen ratio.