高质量立方氮化硼薄膜的射频磁控溅射制备及其性能表征

运用射频磁控溅射法在硅片上制备了立方氮化硼薄膜,并对射频功率、气体分压比及衬底偏压等参数对膜中立方氮化硼(c-BN)含量的影响进行了研究.采用傅立叶红外光谱(FTIR)、拉曼光谱、X射线光电子能谱(XPS)和原子力显微镜(AFM)对c-BN薄膜进行了表征和分析.结果表明:300 W的射频功率是制备c-BN薄膜的最佳条件;当气体分压比Ar/N2=5:1时,制备的薄膜中c-BN含量相对最高;立方氮化硼的形成存在偏压阈值(约80 V),低于此偏压c-BN很难形成.拉曼光谱分析进一步确认了BN薄膜的晶相结构.AFM和XPS分析结果表明c-BN薄膜结晶良好,晶粒尺寸细小,具有很好的化学配比,B原子与N原子的含量比为1:l.     

c-BN薄膜的生长机制

立方氮化硼(c-BN)薄膜因其优异的机械、电学特性而有着广泛的应用前景.本文在大量的实验研究基础上,阐明衬底温度和荷能粒子轰击的重要作用,并综合分析了其他研究者的结果,较全面地论述了c-BN薄膜沉积过程中非晶层和h-BN层的形成以及c-BN相的形核长大机制.     

高速钢基体离子注氮对c-BN薄膜制备的影响研究

采用射频磁控溅射法在离子注氮的高速钢基体上沉积制备c-BN薄膜,主要研究离子注氮层对c-BN薄膜相结构和内应力的影响;采用各种现代分析方法对沉积的薄膜进行了表征分析,包括傅立叶红外光谱(FTIR)、X射线光电子能谱(XPS)和原子力显微镜(AFM)等分析方法;试验结果表明:高速钢基体上离子注氮有利于立方氮化硼含量的提高和薄膜内应力的降低,同时注氮处理的高速钢基体上沉积的薄膜表面形貌平整,结晶性较好.并采用X射线衍射分析(XRD)对高速钢基体的离子注氮层进行了相结构分析,探索研究了离子注氮层对c-BN薄膜生长的影响.     

工作气压对制备立方氮化硼薄膜的影响

本文报道了工作气压对射频溅射法制备立方氮化硼(c-BN)薄膜影响的实验结果.c-BN薄膜沉积在p型Si(100)衬底上,溅射靶为六角氮化硼(h-BN),工作气体为Ar气和N2气混合而成,薄膜的成分由傅里叶变换红外吸收谱标识.结果表明,与射频功率、衬底温度和衬底负偏压一样,工作气压也是影响c-BN薄膜生长的重要参数.要得到一定立方相含量的氮化硼薄膜,必须要有合适的工作气压,否则,薄膜中不能形成立方相.在工作气压为5×10-3乇时,得到了立方相含量在90%以上的立方氮化硼薄膜.     

c-BN薄膜的生长过程和可重复性的研究

用常规射频(RF)溅射系统,采用三步法在p型Si(111)上高重复率地制备出高品质的立方氮化硼(c-BN)薄膜.通过对c-BN薄膜生长过程的分析,找出了传统两步法制备高品质的c-BN薄膜重复率不高的原因.在两步法之前增加了使湍流层结构氮化硼(t-BN)转化为斜方六面体结构的氮化硼(r-BN)的步骤,即将形核过程分也为两步,使重复率显著提高.傅立叶变换红外吸收光谱的结果表明当第一步偏压为180 V,时间为5 min时,得到了立方相含量为85%的c-BN薄膜.     

消息报道

新型耐腐蚀超硬材料—c-BN薄膜自从超硬的金刚石涂层投放市场以来,最近又出现了新的竞争对手。这种新型材料是立体氮化硼(c-BN)。用它制的耐腐蚀涂层的第一批产品,在两年之内可以问世。尽管金刚石比c-BN硬,但是c-BN在其它许多方面,性能优越。与金刚石不同,c-BN可耐多种熔融的金属,并且它象铝一样可以形成氧化物防护层,防止腐蚀。在一定温度下,c-BN可耐酸、碱腐蚀。     

溅射气压和沉积时间对c-BN薄膜结构的影响

采用磁控反应溅射方法，在Si(100）衬底上沉积c-BN薄膜，研究了溅射气压和沉积时间对薄膜结构的影响。结果表明，随溅射气压的升高或沉积时间的增加，都是削弱荷能粒子对衬底表面的轰击效果，并导致薄膜中c-BN相含量的减小。     

钛酸锶钡薄膜掺杂改性研究进展

钛酸锶钡(BaxSr1-xTiO3,BST)薄膜具有优良的铁电、介电性能,在可调谐微波器件、动态随机存储器、红外探测器阵列等方面具有良好的应用前景.综述了近年来BST薄膜掺杂改性研究所取得的进展,特别是对晶格掺杂和晶界掺杂进行了较详细的评述,并对目前BST薄膜掺杂研究的几个前沿问题进行了详细的讨论.     

BST铁电薄膜的制备及其性能的研究进展

Ba1-xSrxTiO3铁电薄膜具有优良的介电性、铁电性、热释电性,得到了广泛的研究,近年来取得了很多进展.简介了BST材料的结构,并综述了BST薄膜的制备方法及BST薄膜的性能测试和影响铁电性能的几个因素.     

有机铁电薄膜的研究进展

有机铁电薄膜材料因具有光电效应、压电效应、铁电等性能,可广泛应用于电子器件而备受关注.综述了聚偏氟乙烯[Poly(vinylidene fluoride)]及其共聚物铁电材料的结构和性能,从有机铁电薄膜的3种疲劳机理和降低疲劳的措施出发,综述了近年来国内外在铁电薄膜电疲劳研究方面所取得的进展,总结了有机铁电薄膜的应用,提出了今后可能开展的工作.     

c—BN薄膜研究进展

立方氮化硼（ｃ－ ＢＮ） 在机械、热、电子及光学方面有许多优异性能,因此世界上有很多研究人员从事ｃ－ ＢＮ 薄膜制备的研究,近年来薄膜沉积技术和ｃ－ ＢＮ 薄膜质量都已取得显著进步。介绍ｃ － ＢＮ 薄膜的用途、结构、制备方法及存在的问题。重点总结了控制ｃ－ ＢＮ 相形成的关键因素及ｃ－ ＢＮ 相形成机理。     

Cubic phase content and structure of BN films from an X-ray absorption study

X-ray absorption near-edge structure (XANES) was used to study the cubic boron nitride (c-BN) content in the BN films deposited on various substrates by different physical vapor deposition or plasma-enhanced chemical vapor deposition methods. By fitting the XANES curves of thin-film samples using standard spectra of pure c-BN and sp(2)-bonded BN in the films with suitable weight factors, the c-BN contents at the film's surface region and across the film's thickness have been determined quantitatively. The results agree well with the previous transmission electron microscopic observations. The method is proved to be independent of the optical properties of thin film and provides a possibility to evaluate the cubic content of BN films accurately.     

Epitaxy of cubic boron nitride on (001)-oriented diamond

Cubic boron nitride (c-BN), although offering a number of highly attractive properties comparable to diamond, like hardness, chemical inertness and a large electronic bandgap, up to now has not found the attention it deserves. This mostly has to do with preparational problems, with easy chemical routes not available and, instead, the necessity to apply ion-bombardment-assisted methods. Hence, most of the c-BN samples prepared as thin films have been nanocrystalline, making the prospect of using this material for high-temperature electronic applications an illusion. Although heteroepitaxial nucleation of c-BN on diamond substrates has been demonstrated using the high-pressure-high-temperature technique, none of the low-pressure methods ever succeeded in the epitaxial growth of c-BN on any substrate. Here, we demonstrate that heteroepitaxial c-BN films can be prepared at 900 degrees C on highly (001)-oriented diamond films, formed by chemical vapour deposition, using ion-beam-assisted deposition as a low-pressure technique. The orientation relationship was found to be c-BN(001)[100]||diamond(001)[100]. High-resolution transmission electron microscopy additionally proved that epitaxy can be achieved without an intermediate hexagonal BN layer that is commonly observed on various substrates.     

Mechanism of nucleation and growth of cubic boron nitride thin films

The mechanism and the crystallography of the nucleation and growth of cubic boron nitride (c-BN) films deposited on 〈100〉-oriented silicon substrate by RF bias sputtering have been studied by means of cross-sectional high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Both methods provide experimental information showing no sp²-bonded BN layer formation in the subsurface region of c-BN phase. This is clear evidence for layer-by-layer homoepitaxial growth of cubic boron nitride without graphitic monolayers in the near-surface region of the film. The turbostratic boron nitride (t-BN) consists of thin sub-layers, 0.5–2 nm thick, growing in such a way that a sub-layer normal is almost parallel to the growth direction. t-BN also comprises a large volume fraction of the grain boundaries with high interface energies. The present result and the finding by Shtansky et al. [Acta Mater. 48, 3745 (2000)], who showed that an individual sub-layer consists of parallel lamellae in both the hexagonal +h-BN) and rhombohedral (r-BN) configurations, demonstrate that high intrinsic stress in the films is due to the complex structure of sp²-bonded BN. The crystallography of c-BN films indicates heteroepitaxial nucleation of cubic phase on the graphitic BN structural precursor. The present results are consistent with stress-induced c-BN formation.     

Cubic boron nitride based metastable coatings and nanocomposites

Various PVD and plasma-assisted CVD methods presently used for the deposition of cubic boron nitride (c-BN) thin films demand adequate conditions relating to ion bombardment of growing films, growth temperature, film stoichiometry, etc. The deposition conditions, often appearing rather apparatus-dependent, can be well categorized according to the fundamental parameters of bombarding ions as well as condensing neutral particles, including their energy and flux ratio, and a few of others like ion mass and incident angle. According to these parameters, various surface kinetic processes and their consequences are discussed particularly in connection with the resulting film phases and stress. Typical c-BN films are known for their extremely high compressive stress and poor adhesion as a result of intensive ion bombardment during deposition. Individual measures attempting to relieve this detrimental stress are briefly summarized. The present paper focuses on magnetron-sputtered, c-BN-based metastable films and nanocomposite films with considerably reduced internal stress in comparison to the usual “pure” c-BN films. Two examples will be shown, namely c-BN/a-C nanocomposite and c-BN:O metastable films, including their deposition details, structure and composition characterization, and mechanical properties. Also illustrated is a growth scheme tailored for the deposition of thick, adhered, cubic-phase dominated, superhard c-BN:O films above 2 µm on silicon substrates.     

Preparation of c-BN films by RF sputtering and the relation of BN phase formation to the substrate bias and temperature

This paper deals with the deposition of cubic boron nitride (c-BN) films by radio frequency (RF) magnetron sputtering. The nearly pure c-BN films have been prepared on Si(100) substrates using hexagonal boron nitride (h-BN) targets. Argon gas mixed with nitrogen gas was used as sputtering gas. The deposited films were characterized by Fourier transform infrared (FTIR) spectroscopy and transmission electron diffraction (TED). A ‘temperature-bias' phase diagram has been worked out. It indicates that the c-BN phase prefers the relative high temperature and negative bias. An opinion was presented that the c-BN nuclei grow discontinuously with every time the ‘thermal spike' coming.     

Comparison of the properties of BN films synthesized by inductively coupled r.f. and microwave plasmas

Thin films of boron nitride are synthesized by two plasma-enhanced chemical vapour deposition techniques: inductively coupled r.f. plasma (13.56 MHz) and microwave plasma (2.45 GHz). We study the composition (impurity level, B/N ratio), the proportion of c-BN phase in the films and other properties of those films as a function of various process parameters. Two boron and two nitrogen precursors are compared: trimethyl borazine and diborane, dini trogen and ammonia, respectively. The advantages and disadvantages of each combinations are presented. The deposition process is followed by optical emission spectroscopy. Adhesion is one of the main problems encountered for films containing c-BN.     

Thick c-BN coatings - Preparation, properties and application tests

Due to the outstanding properties of cubic boron nitride (c-BN) - c-BN is the second hardest of all known materials, has a high wear resistance and a high thermal stability - this material is very promising for a broad range of applications, especially for cutting tools, both as bulk and as a coating material. The state-of-the-art is the use of sintered cutting inserts with c-BN grains. Such c-BN grains are synthesized in an expensive high-pressure-high-temperature process.The requirements for cutting tools continuously increase in production engineering and this leads to a strong demand for new super hard tool coatings. Cubic boron nitride coatings could be an attractive solution. Unfortunately, the preparation of thick c-BN coatings, on the μm scale, is difficult, due to some serious drawbacks and has been successful only in the last years for a few research groups worldwide.PVD processes allow the preparation of c-BN films thicker than 2 μm on silicon and 1 μm c-BN top layers on pre-coated cemented carbide cutting inserts. Measurements of mechanical properties like hardness and Young's modulus reveal that the properties of the c-BN coatings, with hardness of about 60 GPa, are nearly identical to those of c-BN bulk material.Results of systematic turning and milling tests of different coatings in combination with a c-BN top-layer on cemented carbide cutting inserts will be presented in detail. The new results confirm the high potential of c-BN coatings on cutting tools.     

Structural evolution of boron nitride films grown on diamond buffer-layers

Boron nitride films on diamond buffer layers of varying grain size, surface roughness and crystallinity are deposited by the reaction of B₂H₆ and NH₃ in a mixture of H₂ and Ar via microwave plasma-assisted chemical vapor deposition. Various forms of boron nitride, including amorphous α-BN, hexagonal h-BN, turbostratic t-BN, rhombohedral r-BN, explosion E-BN, wurzitic w-BN and cubic c-BN, are detected in the BN films grown on different diamond buffer layers at varying distances from the interface of diamond and BN layers. The c-BN content in the BN films is inversely proportional to the surface roughness of the diamond buffer layers. Cubic boron nitride can directly grow on smooth nanocrystalline diamond films, while precursor layers consisting of various sp²-bonded BN phases are formed prior to the growth of c-BN film on rough microcrystalline diamond films.     

Mechanism of nucleation and growth of cubic boron nitride thin films

The mechanism and the crystallography of the nucleation and growth of cubic boron nitride (c-BN) films deposited on 100-oriented silicon substrate by RF bias sputtering have been studied by means of cross-sectional high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Both methods provide experimental information showing no sp²-bonded BN layer formation in the subsurface region of c-BN phase. This is clear evidence for layer-by-layer homoepitaxial growth of cubic boron nitride without graphitic monolayers in the near-surface region of the film. The turbostratic boron nitride (t-BN) consists of thin sub-layers, 0.5–2 nm thick, growing in such a way that a sub-layer normal is almost parallel to the growth direction. t-BN also comprises a large volume fraction of the grain boundaries with high interface energies. The present result and the finding by Shtansky et al. [Acta Mater. 48, 3745 (2000)], who showed that an individual sub-layer consists of parallel lamellae in both the hexagonal (h-BN) and rhombohedral (r-BN) configurations, demonstrate that high intrinsic stress in the films is due to the complex structure of sp²-bonded BN. The crystallography of c-BN films indicates heteroepitaxial nucleation of cubic phase on the graphitic BN structural precursor. The present results are consistent with stress-induced c-BN formation.