【作者】 柯贤文；

【导师】 付德君；

【作者基本信息】 武汉大学 ， 粒子物理与原子核物理， 2011， 博士

【摘要】 本论文用反应离化团簇束沉积和磁控溅射制备了ZnO和ZnMnO薄膜,用离子注入方法对薄膜进行了不同元素和不同剂量的掺杂,对样品的结构、成分、光学性质、磁学性质进行了系统的实验研究。1、ZnO薄膜制备。在反应离化团簇束(RICB)法制备ZnO薄膜的实验中,采用自行设计的RICB系统,以Hall离子源为基础,增加了超声坩埚和气体引入孔,发展成一套团簇离子束沉积装置。制备的薄膜用X射线衍射和EDS能谱进行了测试分析,结果表明薄膜具有的C轴择优取向,膜中氧、锌原子比接近1：1。用磁控溅射技术在Si(111)上沉积了ZnMnO薄膜,溅射中使用的靶材为ZnO:Mn (Mn的重量比为5%)。XRD衍射谱中没有发现Mn的氧化物,说明Mn以替位的形式取代了Zn的晶格位置。ZnMnO样品的XPS光谱测量表明薄膜中的Zn主要是以Zn2+的化合态形式存在。此外,XPS光谱测量结果也表明了薄膜中几乎没有多余的锌存在,在Mn掺杂的ZnO薄膜中,Mn作为杂质替换了Zn的晶格位置。ZnMnO薄膜的拉曼散射光谱表明样品的所有峰都是ZnMnO的特征峰。另外在我们ZnMnO样品的Raman光谱中均未发现MnO、Mn3O4或者MnO2。说明薄膜中Mn并没有以其他氧化物的形式存在。2、ZnO的离子注入掺杂。用Sb离子注入方法对采用PLD方法在蓝宝石衬底上沉积的ZnO薄膜进行了掺杂。离子注入能量为200KeV,注入剂量分别为5x1013,5x1014,1x1015,1x1016cm-2。注入后的样品在氧气气氛中分别在400、500和600℃下进行快速热退火。注入剂量较低时,576cm-1峰强度有较大幅度的增强,并且在位于550cm-1处的肩形中心出现较宽的不对称半高宽。这可能是离子注入引起的晶格损伤,因为这种非对称性在快速热退火后消除了,表明一定浓度的杂质离子已经使ZnO晶格的576cm-1峰对应的波矢面上的晶格结构产生了缺陷。实验发现,要完全消除该缺陷,600℃的退火温度是必须的。注入剂量较高时,在ZnO薄膜的拉曼光谱中,位于576cm-1处的峰得到增强并且半高宽(FWHM)也增加了,通过热退火后晶格损伤的恢复非常微弱,发现退火对改善576cm-1峰的半高宽非对称化以及降低峰高并没有什么明显的帮助。表明高剂量的离子注入导致了晶格的严重损伤,sb离子到这个浓度时,576cm-1峰对应的波矢面上的晶格结构损伤已经比较严重。通过对照比较不同注入剂量的样品可以清楚地看到,576cm-1峰随着Sb离子注入剂量的增大,峰高增高,半高宽变宽,非对称性化更明显。在Sb离子注入的ZnO PL光谱中存在峰3.230 eV,它在未注入样品中未被观察到。这可能是由于Sb离子的注入引起的,并且是作为受主存在的。在Sb离子注入后所有PL峰的强度都发生了变化,3.365 eV峰相对3.331 eV峰得到了增强,但所有的峰相对于未注入前都减弱了,表明高能离子辐照对Zn0光学性质的影响。用Sb离子注入方法对磁控溅射沉积的ZnMnO薄膜进行了掺杂,离子注入能量为200 keV,注入剂量分别为5×1013,5×1014,1×1015,1×1016cm2。在样品的XPS光电子能谱中,位于薄膜表面的01s峰被高斯拟合为两个峰,其中心分别位于529.8和531.2 eV。位于1021.3eV的Zn 2p3/2峰表明薄膜中的Zn主要是以Zn2+的化合态形式存在。Zn 2p3/2峰良好对称性说明薄膜中没有过量的Zn存在。ZnMnO薄膜中位于642.1 eV的Mn 2p2/3的XPS光谱,说明在Mn掺杂的Zn0薄膜中,Mn作为杂质替换了Zn的晶格位置,并且Mn主要以Mn2+的氧化物形式存在。ZnMnO薄膜XRD谱没有发现Mn或者Sb的氧化物形式存在,说明Mn和Sb以替位的形式取代了Zn的晶格位置。在Sb离子注入的ZnMnO薄膜的XRD衍射谱中(101)峰非常弱并且在在40°附近可以观察到一无定形带,是离子轰击引起的晶格失配造成的。3、过渡金属离子注入及其磁性研究。用Mn离子注入对用PLD方法在Si(111)衬底上生长ZnO的薄膜进行了掺杂,注入能量为200 keV,注入剂量分别为1×1015,5×1015,1×1016和5×1016 ions/cm2。注入前ZnO外延层的(002)峰位为34.62°,注入样品的峰位为34.47°,经400,550和700℃退火后,峰位分别移到34.65,34.76和34.67°。随着Mn离子注入剂量不同,(002)峰的散射角度和半高宽有明显的变化。用Scherrer公式计算Mn离子注入剂量分别为1x1015,5×1015,1×1016和5x1016ions/cm2的薄膜中晶体的尺寸依次为156,77,63和56 nm。Mn注入导致ZnO的A1(LO)和E2(high)峰变宽,且向低频方向移动,这是由于离子注入引起的晶格损伤造成的。同时存在两个额外声子模式619(I1)和642 cm-1(I2),是与杂质相关的复合体或主缺陷引起的本征振动模式。AFM测试表明,Mn离子的剂量从1×1015 ions/cm2增加到5×1016 ions/cm2时,样品的粗糙度从29.9 nm增加到51.5nm。光致发光测试表明,未注入ZnO薄膜的PL光谱中在3.25 eV处存在一强烈的近带边发射峰；由于氧空位或间隙原子的存在,在未注入的ZnO样品中没有发现绿光或黄光发射峰,说明未注入的ZnO薄膜具有良好的晶体质量。在Mn注入的ZnO薄膜发现了大约位于540nm处的黄光带,同时,近带边发射峰向低能量方向移动,这是由于Mn离子的引入而引起的张应力所造成的结果。测量了ZnO:Mn薄膜的磁滞回线,测试时磁场平行于样品表面。在300K的温度下磁场强度高于2k0e时,样品的磁化强度达到饱和,当Mn原子的摩尔比为5%时出现最大剩磁强度。由于在样品中并没有观察到可能的MnO或MnO2第二相存在,因此样品的磁性并不是来自于Mn的氧化物。更多还原

【Abstract】 In this thesis, ZnO and ZnMnO thin films have been prepared by reactive ionized cluster beam, magnetron sputtering and pulsed laser deposition. Ion implantation with different elements and different dose is used to dope the films. Finally a series of analysis and research have been carried out on the structure, composition,optical and magnetic characterization.1. Deposition of ZnO films. Reactive ionized cluster beam (RICB) is used to prepared ZnO Thin Films. We design the RICB system and in the system, we use a Hall ion sourse, add an ultrasonic crucible and a gas introduction holl, on the basis of these, a set of RICB has been combined. X-ray diffraction (XRD) and EDS energy spectroscopy are used to test and analyse the samples. Results show that films are of wurtzite structure along the C-axis orientation growth characteristics and better crystal quality, while the atomic ratio of ZnO thin films is close to 1:1.ZnMnO films are deposited on silicon Si (111) substrates by magnetron sputtering, sputtering targets are ZnO:Mn (Mn weight ratio is 5%). Mn oxides form is not be found in the XRD spectra, indicating that Mn has substituted Zn lattice position. XPS spectra of the ZnMnO films indicate the dominant oxidation state is Mn2+. And the XPS spectra reveal that Mn as dopant substitutes the lattice position of Zn and there are no excessive Zn exiting in the Mn-doped ZnO film. The peaks of ZnMnO film Raman scattering are all the ZnMnO characteristic peaks. MnO, Mn3O4 or MnO2 are not found in Raman spectra, Indicating that there are no other Mn oxides in our ZnMnO samples.2.Ion implantation doping of ZnO film. ZnO films were grown on Si (111) by pulsed-laser deposition. Doping was conducted by 200 keV Sb implantation to total doses of×1013,5×1014, 1×1015,1×1016cm-2. Rapid thermal annealing was carried out at temperatures of 400,500,600℃for 30 s in a flowing oxygen atmosphere. When the implantation dose is lower, the peak at 576 cm-1 experiences an increase and has an asymmetric shape with a shoulder centered at 550 cm-1. This is attributed to ion-induced damage to the lattice, since this asymmetric band has been eliminated after the rapid thermal annealing. We found that to completely remove the defects, an annealing temperature of 600℃is necessary. When implantation dose is higher, in the Raman spectra of ZnO thin films, the peak at 576 cm-1 is enhanced and half width (FWHM) also increased. After thermal annealing, the recovery of lattice damage is very weak and found that annealing to improve the 576 cm" peak FWHM and lower non-symmetric peak has no apparent help. This shows that high doses of ion implantation resulted in serious injury lattice, Sb ions to this concentration,576 cm-1 peak corresponding to the wave vector surface of the crystal lattice structure damage have been more serious. Through comparisons of the different doses of the sample can be clearly seen,576cm-1 peak with the Sb ion implantation dose increases, the peak height increased, the FWHM broadening, asymmetry of the more obvious. In the Sb ion implantation in ZnO films PL spectrum there is 3.230 eV peak, and it is not observed in un-doped samples. This may be caused by the Sb ion implantation, and Sb as acceptors exist in the films. The PL peaks intensity of all Sb ion implantation samples have changed, and the peak of 3.365 eV relative to the peak of 3.331 eV peak has been enhanced, but all of the peaks relative to the un-doped samples were weakened, indicating that high energy ion implantation effects on the optical properties of ZnO.ZnMnO films were grown on Si (111) by magnetron sputtering. Doping was conducted by 200 keV Sb implantation to total doses of 5×1013,5×1014, 1×1015, 1×1016 cm-2. In the XPS spectra of ZnMnO films, The typical Ols peak in the surface can be fitted two peaks by nearly Gaussian functions. The Zn 2p3/2 peak is situated at 1021.3eV, showing that Zn ion in the films are mainly in the chemical states of Zn2+. The core level spectrum of Zn 2p3/2 shows good symmetry. These results indicate that there is little excessive zinc existing in the films. Mn 2p2/3 XPS spectra for the ZnMnO films located at about 642.1 eV. This is the peak position of the binding energy of Mn2+ oxid. Mn as dopant substitutes the lattice position of Zn in the Mn-doped ZnO film. The symmetry indicates a single bonding state of Mn in ZnMnO films. In the X-ray diffraction pattem of the Sb-implanted ZnMnO films, (101) peak is very weak and one amorphous zone can be observed near the 40°, it is obviously due to the mismatch of lattice caused by ion bombardment.3. Transition metal ion implantation and magnetism research. ZnO films were grown on Si (111) by pulsed-laser deposition. Doping was conducted by 200 keV Sb implantation to total doses of 1x1015,5x1015,1x1016,5x1016 cm-2. The 2θvalues of (002) peaks are in the range of 34-35°:the peak of the ZnO epilayer is located at 34.62°. The value of the implanted ZnO is at 34.47°. After annealing at 400,550and 700℃, the peak moves to 34.65,34.76 and 34.67°respectively. Changes in the diffraction angle and full width at half maximum (FWHM) of the prominent (002) peak are observed in samples implanted with different Mn doses. Both the A1 (LO) and E2 (high) modes of the as-implanted ZnO film are broadened and shifted towards the low-frequency side, compared with the values of bulk ZnO. This is attributed to ion-induced damage to the lattice. In addition, two additional phonon modes at 619 (I1) and 642 cm-1 (I2) were observed in ZnO:Mn thin films,which were ascribed to local vibration modes due to dopant-related complexes or to host defects. The surfaces of the as-deposited ZnO and implanted ZnO:Mn thin films were investigated using AFM. It is clearly seen that the surface of implanted ZnO tends to be compact and homogeneous and quite different from that of the as-deposited sample; micro-particles are dispersed evenly throughout the modified surface, whereas no such small particles appear on the as-deposited sample. For the annealed sample implanted with Mn+ ions dose above 1×106 cm-2, we notice numerous clusters with a regular shape and uniformly distributed in the sample. We also measured the root mean square (RMS) roughness and the results showed that the RMS roughness decreased from 29.9 nm to 51.5 nm when the implantation dose of Mn increased from 1×1015 to 5×1016 ions/cm2. The PL spectrum of as-deposited ZnO consists of strong near-band edge (NBE) emission peak at 3.25 eV; no yellow or green emission peaks due to ionized oxygen vacancy or interstitial atoms are observed. This indicates the good crystalline quality of the as-deposited ZnO films. In the Mn implanted ZnO film, however, we observe a yellow band around 540 nm. The near-bandedge emission position is also shifted to lower energy, which can be attributed to strain induced by the incorporation of Mn ions, which have a larger ionic radius than Zn and would expand the lattice when substituting Zn sites. Magnetization loops of the implanted ZnO:Mn films were measured at room temperature with the magnetic field being applied parallel to the surface of the samples. The hysteresis loop was measured at 300K of the magnetic ZnO:Mn with Mn implantation dose of 5×1016 ions/cm2. The magnetization of the sample is saturated for fields higher than 2 kOe at 300 K. In our experiment, a maximum remnant magnetization is observed in samples with 5 mol% Mn. Since the possible secondary phases like MnO and MnO2 were not observed, it is understood that the observed magnetic behavior in ZnO:Mn films are not due to formation of the manganese oxides.更多还原