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.

Optical properties of hexagonal boron nitride thin films deposited by radio frequency bias magnetron sputtering

The optical properties of hexagonal boron nitride （h-BN） thin films were studied in this paper. The films were characterized by Fourier transform infrared spectroscopy, UV-visible transmittance and reflection spectra, h-BN thin films with a wide optical band gap Eg （5.86 eV for the as-deposited film and 5.97 eV for the annealed film） approaching h-BN single crystal were successfully prepared by radio frequency （RF） bias magnetron sputtering and post-deposition annealing at 970 K. The optical absorption behaviour of h-BN films accords with the typical optical absorption characteristics of amorphous materials when fitting is made by the Urbach tail model. The annealed film shows satisfactory structure stability. However, high temperature still has a significant effect on the optical absorption properties, refractive index n, and optical conductivity σ of h-BN thin films. The blue-shift of the optical absorption edge and the increase of Eg probably result from stress relaxation in the film under high temperatures. In addition, it is found that the refractive index clearly exhibits different trends in the visible and ultraviolet regions. Previous calculational results of optical conductivity of h-BN films are confirmed in our experimental results.

In situ infrared spectroscopic study of cubic boron nitride thin film delamination

This paper investigates the procedure of cubic boron nitride （cBN） thin film delamination by Fourier-transform infrared （IR） spectroscopy. It finds that the apparent IR absorption peak area near 1380cm^-1 and 1073 cm^-1 attributed to the B-N stretching vibration of sp2-bonded BN and the transverse optical phonon of cBN, respectively, increased up to 195% and 175% of the original peak area after film delamination induced compressive stress relaxation. The increase of IR absorption of sp2-bonded BN is found to be non-linear and hysteretic to film delamination, which suggests that the relaxation of the turbostratic BN （tBN） layer from the compressed condition is also hysteretic to film delamination. Moreover, cross-sectional transmission electron microscopic observations revealed that cBN film delamination is possible from near the aBN（amorphous BN）/tBN interface at least for films prepared by plasma-enhanced chemical vapour deposition.

Influence of oxygen on the growth of cubic boron nitride thin films by plasma-enhanced chemical vapour deposition

Cubic boron nitride thin films were deposited on silicon substrates by low-pressure inductively coupled plasmaenhanced chemical vapour deposition. It was found that the introduction of 02 into the deposition system suppresses both nucleation and growth of cubic boron nitride. At a B2H6 concentration of 2.5% during film deposition, the critical O2 concentration allowed for the nucleation of cubic boron nitride was found to be less than 1.4%, while that for the growth of cubic boron nitride was higher than 2.1%. Moreover, the infrared absorption peak observed at around 1230- 1280 cm^-1, frequently detected for cubic boron nitride films prepared using non-ultrahigh vacuum systems, appears to be due to the absorption of boron oxide, a contaminant formed as a result of the oxygen impurity. Therefore, the existence of trace oxygen contamination in boron nitride films can be evaluated qualitatively by this infrared absorption peak.

The Adhesion Improvement of Cubic Boron Nitride Film on High Speed Steel Substrate Implanted by Boron Element

Cubic boron nitride(c-BN) films were deposited on W6Mo5Cr4V2 high speed steel(HSS) substrate implanted with boron ion by RF-magnetron sputtering. The films were analyzed by the bending beam method, scratch test, XPS and AFM. The experimental results show that the implantation of boron atom can reduce the internal stress and improve the adhesion strength of the films. The critical load of scratch test rises to 27.45 N, compared to 1.75 N of c-BN film on the unimplanted HSS. The AFM shows that the surface of the c-BN film on the implanted HSS is low in roughness and small in grain size. Then the composition of the boron implanted layer was analyzed by the XPS. And the influence of the boron implanted layer on the internal stress and adhesion strength of c-BN films were investigated.

A Bilayer High-Temperature Dielectric Film with Superior Breakdown Strength and Energy Storage Density

The further electrification of various fields in production and daily life makes it a topic worthy of exploration to improve the performance of capacitors for a long time,including thin-film capacitors.The discharge energy density of thin-film capacitors that serves as one of the important types directly depends on electric field strength and the dielectric constant of the insulation material.However,it has long been a great challenge to improve the breakdown strength and dielectric constant simultaneously.Considering that boron nitride nanosheets(BNNS)possess superior insulation and thermal conductivity owing to wide band gap and 2-dimensional structure,a bilayer polymer film is prepared via coating BNNS by solution casting on surface of polyethylene terephthalate(PET)films.By revealing the bandgap and insulating behavior with UV absorption spectrum,leakage current,and finite element calculation,it is manifested that nanocoating contributes to enhance the bandgap of polymer films,thereby suppressing the charge injection by redirecting their transport from electrodes.Worthy to note that an ultrahigh breakdown field strength(~736 MV m^(−1)),an excellent discharge energy density(~8.77 J cm^(−3))and a prominent charge-discharge efficiency(~96.51%)are achieved concurrently,which is ascribed to the contribution of BNNS ultrathin layer.In addition,the modified PET films also have superior comprehensive performance at high temperatures(~120°C).The materials and methods here selected are easily accessible and facile,which are suitable for large-scale roll-to-roll process production,and are of certain significance to explore the methods about film modification suitable for commercial promotion.

Thermally Conductive Polyimide/Boron Nitride Composite Films with Improved Interfacial Compatibility Based on Modified Fillers by Polyimide Brushes

Polyimide-based composite films with high thermal conductivity,good mechanical property and electrical insulating performance are urgently needed in the electronics and microelectronics fields.As one of the key technical challenges to be solved,interfacial compatibility between filler and matrix plays an important role for composite film.Herein,boron nitride was modified by grafting polyimide brushes via a twostep method,and a series of thermally conductive polyimide/boron nitride composite films were prepared.Both characterization and performance results proved that the interfacial interaction and compatibility was greatly enhanced,resulting in a significant reduction in defects and interfacial thermal resistance.The interphase width of transition zone between two phases was also efficiently enlarged due to polyimide brushes grafted on filler surface.As a result,composite films based on polyimide-grafted boron nitride exhibited significantly improved properties compared with those based on pristine filler.Tensile strength can reach up to 80 MPa even if the filler content is as high as 50 wt%.The out-of-plane and in-plane thermal conductivity of composite film increased to 0.841 and 0.850 W·m^(-1)·K^(-1),respectively.In addition,thermal and dielectric properties of composite films were also enhanced to some extent.The above results indicate that surface modification by chemically grafting polymer brushes is an effective method to improve two-phase interfacial compatibility so as to prepare composite film with enhanced properties.

含有氮化硼势垒层的三明治结构聚合物基复合介质储能特性研究

聚合物基高温储能介质因其较高的功率密度及优异的充放电效率被广泛应用在电气和电子等领域。该文选用不同粒径的氮化硼纳米片(BNNSs)作为填料,掺杂到聚醚酰亚胺(PEI)中构建势垒层,添加在纯PEI两侧制备拥有三明治结构的复合薄膜,探究粒径大小在不同温度/填充体积分数下对复合薄膜的介电性能及储能性能的影响。研究发现,构建BNNSs势垒层的三明治结构复合薄膜显著抑制了介质的高温电导,提高了充放电效率,且较小粒径BNNSs填充势垒层能更有效地提高击穿场强和储能密度,其中掺杂200 nm粒径BNNSs体积分数为5%的复合薄膜在常温下的储能密度可达5.65J/cm^(3),充放电效率高达96%,即使在150℃下,储能密度和充放电效率也可分别达到2.52 J/cm^(3)和95%。通过随机击穿模型阐明了粒径大小及三明治势垒层结构对击穿性能的提升机制。该文提出的含有势垒层的三明治复合结构为高温下复合薄膜储能特性优化提供了新的策略。

Effect of growth temperature on morphology,structure and luminescence of Tb-doped BN thin films

This paper investigates the effect of growth temperature on morphology, structure and photoluminescence （PL） of Tb-doped boron nitride （BN） films grown by magnetron sputtering, and the relationships of growth-temperature- structure-PL by scanning electron microscopy, transmission electron microscopy and PL. The characteristic emission lines of the Tb^3＋ were observed in the PL spectra at room temperature. The 473-K-grown film is mainly consisted of amorphous BN particles. With the growth temperature increasing up to 1273 K, the amount of amorphous BN decreases, while the amount of turbostratic BN increases. Correspondingly, the PL intensities from the Tb^3＋ ions increase with the increase of temperature in the range of 473 1273 K.

Influence of nitrogen implantation into HSS substrate on internal stress and adhesion strength of c-BN films

Cubic boron nitride(c-BN) films were deposited on HSS substrate implanted with nitrogen ion by RF-magnetron sputtering. The films were analyzed by bending beam method, scratch test, XRD and AFM. The results show that the implantation of N ion can reduce the internal stress and improve the adhesion strength of the films.The critical load comes to 16.92N, compared to 1.75N of c-BN film on the unimplanted HSS. AFM shows that the surface of the c-BN film on the implanted HSS is low in roughness and small in grain size. The phase structure of the nitrogen implanted layer was analyzed by XRD. The influence of nitrogen implanted layer on the internal stress and adhesion strength of c-BN films were also investigated.

聚酰胺酸低黏化制备导热BN/PI复合薄膜

为解决填料在高黏度聚酰胺酸(PAA)中易团聚、分散性差的问题,本研究以3,3′,4,4′-联苯四甲酸二酐(BPDA)和对苯二胺(PDA)为原料,采用酸酐水解法在较高固含量下合成了低黏度的聚酰胺酸溶液。在此基础上,通过填料的液相法超声分散预处理和高效球磨混合工艺,制备了氮化硼质量分数为0~40%的氮化硼/聚酰亚胺(BN/PI)复合薄膜,系统考察了填料的分散性以及复合薄膜的力学、耐热、导热等性能。结果表明:聚酰胺酸的低黏化及填料混合分散工艺赋予了填料良好的分散性,并对BN/PI复合薄膜的性能产生重要影响。当填料质量分数为40%时,复合薄膜的力学强度约为140 MPa,玻璃化转变温度为385.2℃,导热系数高达0.741 W/(m·K),相比无填料添加的纯PI膜提高了338%。

六方、立方氮化硼的制备和热传导性质研究进展

随着微电子技术的不断进步,电子芯片集成化电路越来越密集。性能提高的同时,其内部热流密度不断攀升,对电子器件的散热能力提出了更高的要求。低热耗散材料严重制约了电子设备的性能和功效,有效的热传递和热管理已成为下一代微处理器、集成电路、发光二极管等设备稳定工作的重要保障,因此亟需具有更高热导率的半导体材料以提高电子器件的使用寿命。近年来,六方氮化硼(h-BN)和立方氮化硼(c-BN)引起了人们极大的研究兴趣,h-BN具有与石墨类似的层状晶体结构,常被称为“白石墨”,散热、绝缘性能良好;而c-BN为闪锌矿结构,具有类似于金刚石的晶体结构,热导率仅次于金刚石,是第三代半导体中禁带宽度最大的材料。研究表明,2种晶体均具有良好的导热性能,可成为新一代电子芯片散热材料,是当前热管理领域的研究热点。本文对h-BN薄膜和c-BN单晶制备方法的研究进展进行了综述,介绍了h-BN和c-BN热传导性质的研究成果,并对h-BN和c-BN面临的挑战和未来的发展方向进行了展望。

六方氮化硼外延生长研究进展

二维超宽禁带半导体材料六方氮化硼(h-BN)具有绝缘性好、击穿场强高、热导率高,以及良好的稳定性等特点,且其原子级平整表面极少有悬挂键和电荷陷阱的存在,使其有潜力成为二维电子器件的衬底和栅介质材料。实现h-BN应用的关键在于生长高质量的h-BN单晶薄膜,本文详细介绍了在过渡金属衬底、绝缘介质衬底和半导体材料表面外延生长h-BN的方法及其研究进展。在具有催化活性的过渡金属衬底(铜、镍、铁、铂等)上可以外延得到高质量的二维h-BN,而在绝缘介质或半导体材料衬底上直接生长h-BN单晶薄膜更具挑战性。蓝宝石以其良好的热稳定性和化学稳定性成为外延h-BN的首选衬底,蓝宝石衬底上生长h-BN薄膜的方法主要有化学气相沉积、分子束外延、离子束溅射沉积、金属有机气相外延,以及高温后退火等,通过这些方法可以在蓝宝石衬底上外延得到h-BN单晶薄膜,还可以集成到现有的一些III-V族化合物半导体的外延生长工艺之中,为h-BN的大面积应用奠定基础。此外,石墨烯、硅和锗等半导体材料衬底上生长h-BN单晶薄膜也是当前研究的一个热点,这为基于h-BN的异质结制备及其应用提供了新的方向。

热解法在氮化硼基底上沉积碳膜衰减器的工艺研究

螺旋线行波管是一种应用较为广泛的宽频带、高增益行波功率放大器件。衰减器是提高管子性能稳定性的关键部件之一。它不仅可以吸收在管子输入、输出端及切断端传输介质的变化引起的反射波,抑制反射波和向前波叠加引起的自激振荡;而且,可以减小传输电路在输入、输出端及切断端产生的阻抗不匹配的影响,扩宽行波管有效传播的频带宽度;同时可以避免陶瓷杆的上的电荷积累造成的放电或电弧。文章通过低压真空热解正庚烷,调整加热场热子温度、加热时间、腔室气压、气体流动等因素,制备出了满足螺旋线行波管设计要求的碳膜衰减器。主要阐述和验证了碳膜衰减器制备过程中从选材到制备过程中的工艺要求及各因素对碳膜衰减器阻值的影响,为螺旋线行波管碳膜衰减器的制备提供了实验依据。

高品质立方氮化硼薄膜的制备及应用基础研究

采用射频（RF）磁控溅射的方法，成功地在（100）单晶硅片上沉积制备出了高品质的c-BN薄膜，并通过对基片的高能离子束的预处理，有效地改善了c－BN薄膜中因内应力导致的差的附着性能．进一步研究了衬底负偏压、温度与薄膜质量的关系，讨论了薄膜中内应力的状态．在此基础上，深入开展了硬质合金上沉积c-BN薄膜的工作，为c-BN薄膜的实际应用奠定了基础．

立方氮化硼薄膜的制备与表征

在对国内外立方氮化硼薄膜的制备工艺及其表征方法进行了综述的基础上,分析了立方氮化硼膜制备中存在的问题,即薄膜的内应力高,结合强度低,沉积温度高,沉积速率低,以及cBN中SP3键含量不稳定。并提出了今后的研究方向:①cBN膜成核生长机理问题;②低温下大面积、高速生长的异质外延和定向生长问题;③膜基结合问题;④发展新的成膜技术,寻求无毒无污染的反应材料;⑤开发cBN膜的应用。

立方氮化硼薄膜制备与性质研究新进展

立方氮化硼(c-BN)具有优异的物理和化学性质,在力学,光学和电子学等方面有着广泛的应用前景．自上世纪80年代开始,低压沉积c-BN薄膜的研究迅速发展,到90年代中期达到高潮,随后进展缓慢,c-BN薄膜研究转入低潮．近年来,c-BN薄膜研究在几方面取得了突破,如获得与衬底粘附良好、厚度超过1μm的c-BN厚膜;成功实现了c-BN单晶薄膜的异质外延生长;此外,在c-BN薄膜力学性质和过渡层微结构研究方面也取得了进展．本文主要评述最近几年c-BN薄膜研究在以上几方面取得的最新进展．

聚酰亚胺/改性六方氮化硼复合薄膜的耐电晕性能研究

采用硅烷偶联剂Z6020对六方氮化硼(h-BN)进行改性,通过原位聚合法制备聚酰亚胺/改性氮化硼(PI/f-BN)复合薄膜。利用红外光谱仪、自制调频耐电晕装置和宽频介电谱测试仪对复合薄膜进行测试,采用光学显微镜对薄膜耐电晕老化后的击穿孔形貌进行表征。结果表明:在棒板空气间隙为1 mm,脉冲电场强度为50 k V/mm,占空比为50%,频率为20 k Hz的测试条件下,随着f-BN含量的提高,薄膜的耐电晕寿命呈先增加后缩短的趋势。当f-BN含量为15%时,复合薄膜的介电常数最大,耐电晕寿命最长。

等离子体源离子渗氮合成硼碳氮薄膜的研究

采用等离子体源离子渗氮，即低能（1-3keV）、超大剂量（10^(19)～10^(20)ions．cm^(-2)）氮离子注入-同步热扩散技术，在300～500℃处理碳化硼薄膜，合成了硼碳氮三元薄膜．俄歇电子能谱和漫反射富氏变换红外光谱分析表明，合成的硼碳氮薄膜是碳硼比固定，氮含量可控的非晶态薄膜．300℃渗氮的薄膜由sp^2型的硼、碳、氮微区构成，而500℃渗氮的薄膜则由sp^3和sP^2型复合的微区组成．较高的渗氮工艺温度促进sP^3型结构的形成，渗氮工艺时间对薄膜结构的影响不显著．

热丝辅助等离子体化学气相法生长c－BN薄膜

用热丝辅助射频等离子体化学气相沉积法（ＰＣＶＤ）合成：ｃ－ＢＮ薄膜获得成功。实验结果表明，灯丝温度、反应气压、衬底温度、灯丝与衬底距离对薄膜质量有重要影响。