电化学方法制备ZnO纳米颗粒掺杂类金刚石薄膜及其场发射性能研究

采用液相电化学沉积技术制备了ZnO纳米颗粒掺杂的类金刚石(DLC)薄膜, 研究了ZnO纳米颗粒掺杂对DLC薄膜场发射性能的影响. 利用X射线光电子能谱、透射电子显微镜、Raman光谱以及原子力显微镜分别对薄膜的化学组成、 微观结构和表面形貌进行了表征. 结果表明: 薄膜中的ZnO纳米颗粒具有纤锌矿结构, 其含量随着电解液中Zn源的增加而增加. ZnO纳米颗粒掺杂增强了DLC薄膜的石墨化和表面粗糙度. 场发射测试表明, ZnO纳米颗粒掺杂能提高DLC薄膜的场发射性能, 其中Zn与Zn+C的原子比为10.3%的样品在外加电场强度为20.7 V/μm时电流密度达到了1 mA/cm². 薄膜场发射性能的提高归因于ZnO掺杂引起的表面粗糙度和DLC薄膜石墨化程度的增加.     

工作气压对ZnO:Mn薄膜结构特性的影响

利用射频磁控溅射方法在玻璃衬底上沉积了一系列ZnO:Mn薄膜,结合Raman光谱、XRD衍射谱和SEM分析了工作气压对ZnO:Mn薄膜结构特性的影响。Raman拟合光谱显示,在工作气压从1 Pa增加至4 Pa的过程中,ZnO:Mn薄膜始终保持着六角纤锌矿结构。但是,随着气压的降低,对应于E2(High)振动模式的Raman散射峰以及与Mn掺杂相关的特征峰左移,说明在低工作气压时,ZnO:Mn薄膜内晶格缺陷更多,晶格更加无序。这一结论也得到了XRD和SEM结果的证实。     

Mn掺杂对ZnO∶Mn薄膜结构特性的影响

利用射频磁控溅射方法在玻璃衬底上室温沉积了一系列不同Mn掺杂的ZnO∶Mn薄膜。结合Raman光谱,XRD谱和SEM分析了ZnO∶Mn薄膜的结构特性。Raman拟合结果显示,在Mn摩尔分数从0增加到5.6%的过程中,ZnO∶Mn薄膜始终保持着六角纤锌矿结构;随着Mn掺杂浓度的增大,437 cm-1和527 cm-1位置上的Raman散射峰出现红移现象,说明Mn掺杂量的增加导致晶格更加无序,缺陷增多;当Mn摩尔分数达到15.8%时,647 cm-1处的Raman散射峰出现,暗示了MnO的产生,同时薄膜结晶质量变差。这一结论也得到了XRD和SEM结果的支持。     

MOCVD法生长ZnO薄膜的结构及光学特性

采用MOCVD方法在c Al2 O3衬底上生长出了具有单一c轴取向的ZnO薄膜 ,采用X射线衍射 (XRD)、Raman散射、X射线光电子能谱 (XPS)及光致发光 (PL)谱等方法对ZnO薄膜的结构及光学特性进行分析测试。XRD分析只观察到ZnO薄膜 (0 0 0 2 )衍射峰 ,其FWHM数值为 0 1 84°。Raman散射谱中 ,4 35 32cm- 1 处喇曼峰为ZnO的E2 (high)振动模 ,A1 (LO)振动模位于 5 75 32cm- 1 处。XPS分析表明 :ZnO薄膜表面易吸附游离态氧 ,刻蚀后ZnO薄膜O1s光电子能谱峰位于 5 30 2eV ,更接近Zn—O键中O1s电子结合能 (5 30 4eV)。PL谱中 ,在3 2 8eV处观察到了自由激子发射峰 ,而深能级跃迁峰位于 2 5 5eV ,二者峰强比值为 4 0∶1 ,表明生长的ZnO薄膜具有较高的光学质量     

射频辅助N掺杂ZnO薄膜的生长及其光电特性

在MOCVD设备中采用改进的射频辅助生长装置,通过裂解N2及N-Al共掺杂的方法进行ZnO的p型掺杂研究。通过二次离子质谱(SIMS)、X射线衍射(XRD)、原子力显微镜(AFM)、光致发光(PL)谱等方法分析了薄膜中N杂质的浓度,以及射频功率与晶体质量、表面形貌以及光学特性之间的关系,并与Al掺杂和N掺杂的ZnO薄膜进行对比。实验结果表明,N掺杂的浓度高达1020cm-3;N-Al共掺杂极大地增加了ZnO的成核速率,其主要原因是N离化所起的作用;N-Al共掺的ZnO薄膜显示出p型性质,而N掺杂的ZnO薄膜由于N原子处于非激活状态而呈现高阻,这说明N-Al共掺杂对ZnO中N原子的活化起到一定作用。     

不同衬底温度下PLD法制备的氧化锌薄膜的特性

利用GCR-170型脉冲激光器Nd:YAG的三次谐波(355nm),以蓝宝石Al2O3(0001)为衬底,在不同温度下采用脉冲激光沉积法制备了ZnO薄膜.通过原子力显微镜、Raman谱、光致发光谱、红外透射谱、霍尔效应和表面粗糙度分析仪对制备的ZnO薄膜进行了测试.分析了在不同衬底温度下薄膜的表面形貌、光学特性,同时进行了薄膜结构和厚度的测试.研究表明:衬底温度对ZnO薄膜的表面形貌、光学特性、结构特性都是重要的工艺参量,尤其在500℃时沉积的ZnO薄膜致密均匀,并表现出较强的紫外发射峰.     

RF溅射钕掺杂ZnO薄膜的结构与发光特性

通过射频磁控溅射技术在Si(111)衬底上制备了未掺杂ZnO薄膜和Nd掺杂ZnO薄膜。应用XRD分析了ZnO:Nd薄膜的晶格结构,通过AFM观察了ZnO:Nd薄膜的表面形貌。结果表明,Nd掺入了ZnO晶格中,由于Nd原子半径大于Zn原子半径,Nd以替位原子的形式存在于ZnO晶格中。ZnO:Nd薄膜为纳米多晶薄膜,表面形貌粗糙。ZnO:Nd薄膜的室温光致发光谱表明,相同条件下制备的未掺杂ZnO薄膜和Nd掺杂ZnO薄膜都出现了395nm的强紫光带和495nm的弱绿光带。我们认为,紫光发射峰窄而锐且强度远大于绿光峰,源于薄膜中激子复合;绿光峰强度较弱,源于薄膜中的氧空位(VO)及氧反位锌缺陷(OZn)。Nd掺杂没有影响ZnO:Nd薄膜的PL谱的发射峰的峰位。由于Nd3 离子电荷数与Zn2 离子电荷数不相等,为了保持ZnO薄膜的电中性,间隙锌(VZn)可以作为Nd替位补偿性的受主杂质而存在,影响ZnO薄膜的激子浓度。同时,Nd掺入使ZnO的晶格畸变缺陷浓度改变增强,因而发射峰的强度随Nd掺杂浓度不同而变化。     

掺Ni的ZnO粉末的Raman光谱研究

利用拉曼(Raman)光谱对掺镍(Ni)氧化锌(ZnO)粉末的声子谱进行了研究.在掺杂样品的Raman光谱中仍能观察到未掺杂ZnO的声子模式,此外还观察到两个额外模式.掺杂粉末中观察到ZnO的E2(h)模式表明掺Ni的ZnO仍然保持六角对称结构.652 cm-1额外模式的起源是掺杂引起的ZnO本底缺陷.为了查明544 cm-1处额外模式的起源,分别对掺Ni,掺钴(Co),和掺锰(Mn)的ZnO粉末的Raman光谱进行了对比研究.结果表明544 cm-1额外模式起源于Ni相关的局域振动模式.对光谱中的其他声子模式的起源也进行了讨论;同时还报告了利用325nm激光作激发源观察到掺Ni样品的多重纵光学(LO)声子模式的结果.     

In掺杂ZnO薄膜的制备及其特性研究

采用射频反应溅射技术在硅(100)衬底上制备了未掺杂和掺In的ZnO薄膜。掠角X射线衍射测试表明,实验中制备的掺In样品为ZnO薄膜。用X射线衍射仪、原子力显微镜和荧光分光光度计分别对两样品的结构、表面形貌和光致发光特性进行了表征,分析了In掺杂对ZnO薄膜的结构和发光特性的影响。与未掺杂ZnO薄膜相比,掺In ZnO薄膜具有高度的C轴择优取向,同时样品的晶格失配较小,与标准ZnO粉末样品之间的晶格失配仅为0．16％;掺In ZnO薄膜表面平滑,表面最大不平整度为7nm。在掺In样品的光致发光谱中观察到了波长位于415nm和433nm处强的蓝紫光双峰,对掺In样品的蓝紫双峰的发光机理进行了讨论,并推测出该蓝紫双峰来源于In替位杂质和Zn填隙杂质缺陷。     

P型半导体氧化锌薄膜的Raman光谱研究

本文主要对超声喷雾热解方法生长在本征Si衬底上的N－In共掺的p型ZnO薄膜的Raman光谱进行了研究。通过洛仑兹(Lorentz)模型和等离子激元与纵光学声子耦合模理论模型拟合不同浓度下的室温Raman光谱, 我们对样品的Raman峰进行了指认; 同时也得到了样品的空穴浓度和迁移率, 结果和霍耳测量得到的空穴浓度和迁移率符合的较好, 证明了霍耳测量p型ZnO薄膜得到的电学参数是可信的。随后我们又对不同浓度的p型ZnO薄膜的变温Raman光谱进行研究,运用一个详细的模型(考虑了晶格热膨胀、残余应力、和三声子、四声子衰变)描述不同浓度下各个样品Raman光谱中的等离子激元与纵光学声子耦合模随温度变化的情况。分析拟合参数, 可以清楚地了解随着浓度的增加耦合模参数随温度的衰变行为。     

Effect of strain on the structural and optical properties of Cu-N co-doped ZnO thin films

Polycrystalline ZnO thin films co-doped with Cu and N have been obtained by chemical bath deposition. Introduction of Cu and N causes the change of strained stress in ZnO films, which subsequently affects the structural and optical properties. The dependence of structural and optical properties of the ZnO films on lattice strained stress is investigated by XRD measurement, SEM, PL spectrum, optical reflection and Raman spectrum. The result of photoluminescence of Cu-N co-doped ZnO films indicates that the UV emission peaks shift slightly towards higher energy side with decrease in tensile strain and vise versa. The blue-shift of the absorption edge and up-shift of E2 (high) mode of the films can be observed in the optical reflection and Raman spectra.     

(Li,Cu)掺杂ZnO薄膜的发光性质

利用溶胶-凝胶(Sol-gel)法在n型si(100)衬底上制备(Li,Cu)掺杂ZnO薄膜,研究了室温下薄膜的结构、形貌和光致发光性能.研究结果表明,随着Li掺杂浓度的增加,可见光发光强度增加,可见光发射可能是源于单电离氧窄位到价带顶以及单电离氧空位到Li替位Zn(Lizn)受主跃迁的双重作用.与此类似,Cu掺杂Zn...     

Electrical properties and Raman scattering investigation of Ag doped ZnO thin films

Ag-doped ZnO thin films were deposited on quartz glass substrates by a radio-frequency (RF) magnetron sputtering technique at room temperature (RT). The influence of Ag doping content on the electrical and Raman scattering properties of ZnO films were systematically investigated by Hall measurement system and Raman scattering spectrum. Two additional local vibrational modes (LVMs) at 230.0 and 394.5 cm^?1 induced by Ag dopant in ZnO:Ag films were observed by Raman analyses at RT, corresponding to Ag atoms located at O sites (LV M_Zn?Ag) and Zn sites (LV M_Ag?O) in ZnO lattice. Moreover, we further studied the effect of donor Ag_O and acceptor Ag_Zn defects on the electrical properties of ZnO:Ag films. The results indicate that O-rich condition is preferred to suppress the formation of Ag_O defects and enhance Ag_Zn defects. The p-type ZnO:Ag film was achieved by properly optimizing the annealing conditions under O-rich condition.     

Effects of hydrogen flow on properties of hydrogen doped ZnO thin films prepared by RF magnetron sputtering

The hydrogen doped ZnO (ZnO:H) thin films were deposited on quartz glass substrates by radio frequency magnetron sputtering. The doping characteristics of ZnO:H thin films with varied hydrogen flow ratio were investigated. At low hydrogen flow ratio (H₂/(H₂+Ar)≤0.02), the ZnO:H thin films exhibited dominant (002) peaks from X-ray diffraction and the lattice constants became smaller. The particles were mainly a columnar structure. The particles’ size became smaller, and the island-like structure appeared on the thin films surface. In addition, the low resistivity properties of ZnO:H thin films was ascribed to the increase of the carriers concentration and carriers mobility; When the hydrogen flow ratio was more than 0.02 (M≥0.02), two absorption bands at 1400–1800 cm^?1 and 3200–3900 cm^?1 were observed from the FT-IR spectra, which indicated that the ZnO:H thin films had typical Zn–H bonding, O–H bonding (hydroxyl), and Zn–H–O bonding (like-hydroxyl). The scanning electron microscope (SEM) results show that a large number of hydroxyl agglomeration formed an island-like structure on the thin films surface. The absorption peak at about 575 cm^?1 in the Raman spectra indicated that oxygen vacancies (V_O) defects were produced in the process of high hydrogen doping. In this condition, the low resistivity properties of ZnO:H thin films were mainly due to the increasing electron concentration resulted from V_O. Meanwhile, the Raman absorption peaks at approximately 98 cm^?1 and 436 cm^?1 became weaker, and the (002) XRD diffraction peak quenched and the lattice constants increased, which shows that the ZnO:H thin films no longer presented a typical ZnO hexagonal wurtzite structure. With the increasing of hydrogen flow ratio, the optical transmittance of ZnO:H thin films in the ultraviolet band show a clear Burstein–Moss shift effect, which further explained that electron concentration was increased due to the increasing V_O with high hydrogen doping concentration. Moreover, the optical reflectance of the thin films decreased, indicating the higher roughness of the films surface. It was noteworthy that etching effect of H plasma was obvious in the process of heavy hydrogen doping.     

SiC缓冲层对Si表面生长的 ZnO薄膜结构和光电性能的改善

用脉冲激光沉积(PLD)技术制备了ZnO/SiC/Si和 ZnO/Si薄膜并制成了紫外探测器。利用X射线衍射(XRD),光致发光(PL)谱,I-V曲线和光电响应谱对薄膜的结构和光电性能进行了研究。实验结果表明:SiC缓冲层改善了ZnO薄膜的结晶质量和光电性能,其原因可能是SiC作为柔性衬底能够减少ZnO与Si 之间大的晶格失配和热失配导致的界面缺陷和界面态。     

低温铝诱导晶化制备纳米晶硅薄膜的物相和光学性能研究

采用射频磁控溅射镀膜系统,在玻璃衬底上制备了非晶硅(α-Si)/铝(Al)复合薄膜,结合氮气(N₂)气氛中低温快速光热退火制备了纳米晶硅(nc-Si)薄膜;利用光学显微镜、共焦光学显微仪、X射线衍射(XRD)仪、拉曼散射光谱(Raman)仪和紫外-可见光-近红外分光光度计(UV-VIS-NIR)对纳米晶硅薄膜的表面形貌、物相及光学性能进行了表征,研究了退火工艺对薄膜性能的影响。结果表明： 300 ℃,25 min光热退火可使α-Si/Al膜晶化为纳米晶硅薄膜,晶化率为15.56%,晶粒尺寸为1.75 nm;退火温度从300 ℃逐渐升高到400 ℃,纳米晶硅薄膜晶粒尺寸、晶化率、带隙逐渐增加,表面均匀性、晶格畸变量逐渐减小;退火温度从400 ℃逐渐升高到500 ℃,纳米晶硅薄膜的晶粒尺寸、晶化率继续增加,带隙则逐渐降低;采用纳米晶硅薄膜的吸光模型验证了所制备的纳米晶硅薄膜的光学特性,其光学带隙的变化趋势与吸光模型得出的结果一致。     

Defects enhanced ferromagnetism in Cu-doped ZnO thin films

We present here new evidences of point defects enhanced ferromagnetism in Cu-doped ZnO thin films by different characterization methods. Cu-doped ZnO thin films with Cu concentrations ranging from 0.05 to 5 at.% were prepared by an inductively coupled plasma enhanced physical vapor deposition system. Room-temperature ferromagnetism is observed in all the films. The saturation magnetization shows an increasing trend with the increase of Cu concentration except a slight decrease for the 1 at.% Cu-doping. Further study performed by Raman spectra, X-ray absorption spectra and extended X-ray absorption fine structure indicate the existence of Cu²⁺ ions and point defects in all the films. The local structural characterization and magnetic properties reveal that the sample with larger saturation magnetization has a higher concentration of point defects.     

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.     

Influence of strain/stress on the nonlinear-optical properties of sprayed deposited ZnO:Al thin films

Nanocrystalline ZnO:Al thin films were deposited by reactive chemical pulverization spray pyrolysis technique on heated glass substrates at 450 °C to study their crystalline structure, composition, strain, stress, roughness characteristics and nonlinear optical susceptibility as a function of Al concentration (0, 2, 3, 5 at.%). The films were characterized by X-ray diffractometer (XRD), EDAX 9100 analyser, atomic force microscopy (AFM) and third harmonic generation (THG). The Al (3 at.%) doped ZnO thin films exhibited the lower strain/stress than undoped films. The nonlinear properties of the ZnO:Al thin films have been found to be influenced by the films strain/stress.     

Effect of irradiating ion fluence on optical properties of ZnO1−x:Nx thin films

Swift heavy ion (SHI) irradiation is an effective technique to modify the optical properties of the materials. In the present investigation, the effect of 100?MeV?Ag⁷⁺ SHI irradiation fluence on the optical properties of ZnO_1?x:N_x thin films was studied. The post irradiation spectroscopic characterizations such as UV–VIS reflectance spectroscopy, Raman spectroscopy and photoluminescence (PL) spectroscopy analysis were carried out. The studies imply that when the SHI passes through the solid, the higher electronic stopping power of ions can weaken oxygen bonds in ZnO, resulting in the formation of donor defects such as oxygen vacancies and zinc interstitials. The formation of donor defects has been acknowledged through the increase in bandgap with irradiating ion fluence. The blue shift observed from the Raman spectra for the 3?×?10¹³ ions/cm² fluence-irradiated films implies the existence of compressive stress in the films. The PL analysis acknowledges the formation of donor defects upon irradiation. Furthermore, it conveys that the presence of N atoms in ZnO lattice leads to the formation of a less number of defects as compared with undoped ZnO while irradiation.