钛酸镧薄膜的制备及工艺优化

为了获得制备钛酸镧（LaTiO3）薄膜的最优工艺条件,采用电子束热蒸发技术在K9基底上制备了单层LaTiO3激光薄膜。研究了不同工艺条件对LaTiO3薄膜激光损伤特性的影响。研究结果表明,对LaTiO3薄膜激光损伤阈值（laser-induced damage threshold, LIDT）影响最大的工艺条件是沉积温度,其次是工作真空度,最后是蒸发束流。获得了制备单层LaTiO3激光薄膜的最优工艺条件:沉积温度175 ℃、工作真空度2.010-2 Pa、蒸发束流120 mA（8 keV）;证明了最优工艺下制备的LaTiO3薄膜具有良好的激光损伤特性、稳定性以及重复性,所制备LaTiO3薄膜的激光损伤阈值为16.9 J/cm2（1 064 nm,10 ns）。     

室温下用脉冲激光沉积E-BN薄膜

 在利用等离子体增强脉冲激光沉积系统沉积立方氮化硼（cBN）薄膜时，发现了氮化硼（BN）材料的E-BN相，并利用扫描电镜和红外吸收光谱及X射线衍射技术对薄膜样品进行了分析，得到了制备较高质量E-BN薄膜的一些热力学参数及时间参数，验证了现有的E-BN结构的形成理论。     

衬底材料对制备立方氮化硼薄膜的影响

较系统地研究了不同衬底材料对制备氮化硼薄膜的影响。用热丝增强射频等离子体CVD法,以NH3,B2H6和H2为反应气体,在Si,Ni,Co和不锈钢等衬底材料上,成功生长出高质量的立方氮化硼薄膜,还用13.56MHz的射频溅射系统将c-BN薄膜沉积在Si衬底上,靶材为h-BN(纯度为99.99％）,溅射气体为氩气和氮气的混合气体,所得到的氮化硼薄膜中立方相含量高于90%,用X射线衍射谱和傅里叶变换红谱对样品进行了分析表明,衬底材料与c-BN的晶格匹配情况,对于CVD生长立方氮化硼薄膜影响很大,而对溅射生长立方氮化硼薄膜影响不大。     

氮化硼薄膜的红外光谱研究

用磁控溅射法制备六角氮化硼薄膜,在衬底温度、衬底偏压、工作气压等条件一定的情况下改变工作气体(氮气+氩气)中氮气的比例,以制备高质量的六角氮化硼薄膜,薄膜以红外吸收光谱标识。实验结果表明,工作气体中氮气的比例对制得的六角氮化硼薄膜有很大影响,在氮气比例为20%时得到理想的六角氮化硼薄膜。     

新型的覆纳米粒子薄膜阴极的研究

采用直流磁控溅射的方法制备出Ir金属纳米粒子薄膜.利用扫描电子显微镜分析了纳米粒子的形态和分布以及不同工艺条件对粒子粒径及形貌的影响,表明纳米粒子的大小可通过调节溅射气体压强来控制.在25%孔度的W海绵基体内浸入6∶1∶2铝酸盐发射物质,然后在其表面沉积上厚度为200—500 nm的纳米粒子薄膜层,最后在H₂气中1200℃烧结,即制成了新型纳米粒子薄膜阴极.利用阴极发射微观均匀性测试仪对纳米粒子薄膜阴极和传统覆膜阴极的热电子发射的均匀性进行了对比研究.采用飞行时间质谱仪测试了真空本底、纳米粒子薄膜阴极、传统覆膜阴极等各种阴极蒸发物的成分,研究了阴极蒸发速率与阴极温度的关系,比较了不同阴极蒸发速率的大小.研究了Ba-W阴极覆上纳米粒子薄膜后的发射特性. 关键词： 纳米粒子薄膜 热阴极 发射均匀性 蒸发     

脉冲直流偏压增强的高质量立方氮化硼薄膜的合成

采用磁增强活性反应离子镀系统成功地合成了立方氮化硼薄膜.通过给基片施加脉冲直流偏压以代替传统的射频偏压,增强了立方氮化硼的成膜稳定性,研究了基片的直流脉冲偏压、等离子体放电电流、通入气体流量比(Ar/N₂)和基片温度沉积参数对立方氮化硼薄膜形成的影响规律.结果表明:随着基片负偏压和放电电流的增大,薄膜中立方氮化硼的纯度提高,当基片负偏压为155V,放电电流为15A时,可获得几乎单相的立方氮化硼薄膜.基片温度为500℃和Ar/N₂流量比为10时,最有利于立方氮化硼 关键词： 立方氮化硼 活性反应离子镀 脉冲偏压     

不同薄膜材料对α束流性能影响的模拟研究

由于回旋加速器引出的束流能量固定,为了满足不同实验对束流能量的不同需求,需要对束流的能量进行调节。为此,研究了利用薄膜材料对束流能量进行改变的可行性。用SRIM程序分析计算了30 MeV α束流(回旋加速器引出能量)穿过金刚石、铝和铜材料后的射程,确定了材料厚度与所需能量之间的关系。利用G4Beamline程序计算了束流经过薄膜后的相空间分布,分析了束流经过不同材料、降低到相同能量(9 MeV)后的横向、纵向发射度的变化,结果显示:束流在经过薄膜材料后,束斑大小几乎不发生改变,束流横向发射度的增长主要由散角的增加引起,其中金刚石薄膜引起的束流发射度增长最小,散角的均方根值约为16 mrad左右,且与初始束流的散角大小没有明显的依赖关系(初始散角均方根值小于1 mrad);不同材料引起的纵向能散均约为1 MeV(半高宽),与材料无关,只与束流的最终能量有关,降能越多,能散越大。此外,对于30 MeV的初始α束流,与金刚石、铜、铝等材料作用后,均会产生约109/μA的中子及γ粒子,在实际应用中应考虑相关的辐射防护问题。     

立方氮化硼薄膜沉积过程的相变研究

从能量和结构两个角度分析了BN四种相的转变过程，以及杂质和缺陷对立方氮化硼(c-BN)薄膜制备的影响.研究了从六角氮化硼(h-BN)到c-BN转变的一个可能的过程，即h-BN→菱形氮化硼(r-BN)→c-BN过程.对纯的h-BN到r-BN的转变需要克服一个很高的能量势垒，在实验室条件下很难能够提供能量来越过这个势垒.而从r-BN到c-BN的转变只需要克服一个很低的能量势垒.这个能量势垒要低于从h-BN到纤锌矿氮化硼(w-BN)转变所需要克服的能量势垒.c-BN薄膜的制备过程中，薄膜在高能粒子轰击下，会产生大量的缺陷，这些缺陷对立方相的形成起到了重要的作用，缺陷和杂质的存在大大降低了从h-BN到r-BN转变的能量势垒.根据这个理论模型，在两步法制备c-BN薄膜的基础上，调整实验参数，形成三步法制备高质量c-BN薄膜.主要研究了三步法中第一步的时间和衬底负偏压对c-BN薄膜制备的影响，找到合适的沉积时间和衬底负偏压分别为5min和-180V.采用三步法制备薄膜，可以重复得到高立方相体积分数(立方相体积分数超过80%)的BN薄膜，并且实验重复性达到70%以上. 关键词： 立方氮化硼 能量势垒 缺陷 衬底偏压     

电子束退火法制备Li-N共掺杂多晶ZnO薄膜

为研究电子束退火对Li-N共掺杂Zn O薄膜性能的影响,首先利用溶胶-凝胶旋涂法在p型Si(111)衬底上制备Li-N共掺杂的Zn O前驱膜,然后用电子束对前驱膜进行退火。退火时,电子束加速电压10 k V,退火时间5 min,聚焦束流123 m A,束流为0.7~1.9 m A,最后得到Li-N共掺杂的Zn O薄膜。XRD谱分析表明,当束流高于1.5 m A之后,薄膜为六方Zn O和立方Zn O的混合多晶薄膜,且有金属Zn生成,导致薄膜有较强的绿光发射。SEM图片分析显示,薄膜的晶粒尺寸随束流增加而增大,当束流高于1.5 m A后,晶粒尺寸变化不大,约为60 nm。光致发光(PL)谱和激光拉曼谱的分析结果证实Li、N元素已掺入Zn O晶格中,PL谱中观察到Li元素掺杂引起的紫光发射,拉曼散射光谱中观察到N替代O位的缺陷振动模式。     

无序双层六角氮化硼量子薄膜的电子性质

基于安德森紧束缚模型,本文研究了无序双层六角氮化硼量子薄膜的电子性质. 数值计算结果表明在双层都无序掺杂的情况下,六角氮化硼量子薄膜的电子是局域的, 其表现为绝缘体性质;而对于单层掺杂(无论是氮原子还是硼原子)的双层六角氮化硼量子薄膜, 在能谱的带尾出现了持续的迁移率边.这就说明在单层掺杂的双层六角氮化硼量子薄膜中产生了 金属绝缘体转变.这一结果证实了有序-无序分区掺杂的理论模型,为理解及调控双层六角氮化硼量子薄膜 的电子性质提供了有益的理论指导.     

Deposition of hexagonal boron nitride thin films on silver nanoparticle substrates and surface enhanced infrared absorption

Silver nanoparticle thin films with different average particle diameters are grown on silicon substrates. Boron nitride thin films are then deposited on the silver nanoparticle interlayers by radio frequency （RF） magnetron sputtering. The boron nitride thin films are characterized by Fourier transform infrared spectra. The average particle diameters of silver nanoparticle thin films are 126.6, 78.4, and 178.8 nm. The results show that the sizes of the silver nanoparticles have effects on the intensities of infrared spectra of boron nitride thin films. An enhanced infrared absorption is detected for boron nitride thin film grown on silver nanoparticle thin film. This result is helpful to study the growth mechanism of boron nitride thin film.     

Structural and phase transformations in thin molybdenum films under stationary irradiation in nitrogen-hydrogen plasma

Structural and phase transformations in thin molybdenum films caused by irradiation in nitrogen-hydrogen arc-discharge plasma are investigated using transition electron microscopy and electron diffractometry. The processing parameters for obtaining thin molybdenum nitride Mo₂N films are determined.     

GaN异质外延的离子化氮源方法

用电离Ｎ_２产生的离子束作为外延生长氮化物的Ｎ源已获得成功，在ＧａＡｓ（１００）衬底上长出了具有立方结晶的ＧａＮ薄膜，其（２００）X射线衍射峰宽仅２３′。并用高分辨率电子能量损失谱测到立方ＧａＮ的表面光学声子出现在损失能量为８２ｍｅＶ处． 关键词：     

Low-temperature synthesis of AlN films through electron cyclotron resonance plasma-aided reactive pulsed laser deposition

Combination of pulsed laser ablation with electron cyclotron resonance microwave discharge was demonstrated for a novel method for low-temperature thin film growth. Aluminum nitride thin films were synthesized on silicon substrates at temperatures below 80 °C by means of reactive pulsed laser deposition in nitrogen plasma generated from the electron cyclotron resonance discharge. The synthesized films show a very smooth surface and were found to have a stoichiometric AlN composition. X-ray photoelectron spectroscopy analysis evidenced the formation of aluminum nitride compound. Fourier transform infrared spectroscopy revealed the characteristic phonon modes of AlN. The AlN films were observed to be highly transparent in the visible and near-IR regions and have a sharp absorption edge near 190 nm. The band gap of the synthesized AlN films was determined to be 5.7 eV. The mechanisms responsible for the low-temperature film synthesis are also discussed in the paper. The nitrogen plasma facilitates the nitride formation and enhances the film growth. Received: 17 March 2000 / Accepted: 28 March 2000 / Published online: 23 May 2001     

FTIR法研究BCN薄膜的内应力

采用射频磁控溅射技术,用六角氮化硼和石墨为溅射靶,以氩气(Ar)和氮气(N2)为工作气体,在Si(100)衬底上制备出硼碳氮(BCN)薄膜。利用傅里叶变换红外光谱(FTIR)考察了不同沉积参数(溅射功率为80~130W、衬底温度为300~500℃、沉积时间为1~4h)条件下制备的薄膜样品。实验结果表明,所制备薄膜均实现了原子级化合。并且沉积参数对BCN薄膜的生长和内应力有很大影响,适当改变沉积参数能有效释放BCN薄膜的内应力。在固定其他条件只改变一个沉积参数的情况下,得到制备具有较小内应力的硼碳氮薄膜的最佳沉积条件:溅射功率为80W、衬底温度为400℃、沉积时间为2h。     

A combined SNMS and EFTEM/EELS study on focused ion beam prepared vanadium nitride thin films

We investigated the diffusion profiles and core-loss fine-structures (ELNES) of thin vanadium nitride films by electron energy-loss spectroscopy (EELS) and energy filtering transmission electron microscopy (EFTEM). The nitride layers have been produced by rapid thermal processing in a NH₃ or N₂ atmosphere and have then been cross-sectioned with a focused ion beam instrument (FIB) under mild milling conditions to maintain crystallography. For the high-resolution electron energy-loss spectroscopy studies (HREELS), a recently developed TEM gun monochromator, implemented into a 200 kV field emission gun column was used in combination with a new post-column spectrometer. It was found that, dependent on substrate and atmosphere, layers with different vanadium and nitrogen content were formed, showing distinct differences in their ELNES. With an energy resolution at the 0.2 eV level and a TEM beam spot size of approximately 2 nm these layers could be unambiguously identified when compared to theoretical ELNES simulations from the literature.     

辉光放电等离子体辅助XeCl准分子激光溅射沉积碳氮薄膜

利用直流辉光放电等离子体辅助的脉冲激光沉积技术在Si衬底上生长了碳氮薄膜.通过扫描电子显微镜、X射线衍射、X射线光电子能谱、俄歇电子能谱等多种手段,对薄膜的形貌、成分、晶体结构、价键状态等特性进行了分析和确定.结果表明,沉积薄膜为含有非晶SiN和晶态氮化碳颗粒结构,晶态成分呈多晶态,主要为α-C₃N₄相、β-C₃N₄相,晶粒大小为40—60nm.碳氮之间主要以C-N非极性共价键形式相结合. 关键词： 脉冲激光沉积 直流辉光放电 碳氮薄膜     

Structural and optoelectronic properties of amorphous GaN thin films

Amorphous gallium nitride (a-GaN) thin films were deposited on glass substrate by electron beam evaporation technique at room temperature and high vacuum using N ₂ as carrier gas. The structural properties of the films was studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). It was clear from XRD spectra and SEM study that the GaN thin films were amorphous. The absorbance, transmittance and reflectance spectra of these films were measured in the wavelength range of 300–2200 nm. The absorption coefficient spectral analysis in the sharp absorption region revealed a direct band gap of E _g = 3:1 eV. The data analysis allowed the determination of the dispersive optical parameters by calculating the refractive index. The oscillator energy E ₀ and the dispersion energy E _d, which is a measure of the average strength of inter-band optical transition or the oscillator strength, were determined. Electrical conductivity of a-GaN was measured in a different range of temperatures. Then, activation energy of a-GaN thin films was calculated which equalled E _a = 0:434 eV.     

Electron and ion beam effects in auger electron spectrometry

In Auger Electron Spectrometry relatively high primary electron current density is usually used in order to obtain a good signal-to-noise ratio. As a consequence, a number of phenomena occurs, which can substantially modify—or even destroy—the sample, and impair the results of the analysis.

In this communication we report some observations on the electron and ion beam interaction on some of the insulating and conducting films used in the silicon device technology. Among the materials considered, silicon nitride and P-doped silicon dioxide are of primary interest, and will be treated in some detail; results on other films, both insulating (Al₂O₃, B-doped SiO₂, etc.) and conducting (Al-Si alloys) will also be reported.

The electron beam causes the oxides (B, Al, Si, P) to be reduced, as shown by the decrease of the height of the low energy, chemically shifted peaks (B_KVV, Al_LVV, Si_Lvv, P_Lvv) and by the contemporary increase of the height of the elemental peaks. In phosphorus doped glasses the electron beam also induces a strong surface P enrichment, followed by a P desorption. Silicon nitride was found to be quite stable against the e-b irradiation in “good” vacuum, but very sensitive to the e-b induced oxidation even at (total) pressure as low as 5 × 10¹⁰ torr. This is a very important fact to be taken into account when evaluating thin Si₃N₄ films, because it can change the apparent film stoichiometry.

Some metallic films are also preferentially oxidized by the electron beam; in Al/Si diluted alloy (0.1÷2% silicon) a strong surface silicon enrichment was found to take phase on small-grained thin films, but not on bulk material.

Our results show that much care has to be taken when performing or interpreting the AES data, and how to use, in some cases, the e-b irradiation effects to increase the sensitivity of the method.