等离子体辅助反应式脉冲激光熔蚀制备AIN薄膜的低温生长

使用等离子体辅助反应式脉冲激光溅射沉积薄膜的方法在Ｓｉ（１１１）和Ｓｉ（１００）基片上已经成功地低温制备出ＡＩＮ多晶膜。实验表明,当脉冲能量密度ＤＥ＝１．０Ｊ·ｃｍ＾－２,脉冲频率ｆ＝５Ｈｚ,氮气气压ＰＮ２＝１．３３×１０＾４Ｐａ,基底温度ｔｓｕｂ＝２００℃,放电电压Ｖ＝６５０,基靶距离ｄｓ－Ｔ＝４ｃｍ时薄膜的生长速度等于６ｎｍ／ｍｉｎ。ＡＩＮ薄膜的折射率为２．０５,和基底的取向关系分别为：ＡＩＮ     

二价离子替代的Nasicon及其应用研究

含二价阳离子的Ｎａｓｉｃｏｎ，Ｍ￣（２＋）Ｎａｓｉｃｏｎ（Ｍ＝Ｍｇ、Ｃａ、Ｓｒ、Ｚｎ）可由母体Ｎａ＿３Ｚｒ＿２Ｓｉ＿２ＰＯ＿（１２）（Ｎａｓｉｃｏｎ）为起始原料与相应的二价离子的盐浓液或熔盐进行离子交换而制得。Ｘ射线衍射分析结果表明离子交换后的产物Ｍ￣（２＋）－Ｎａｓｉｃｏｎ大多保持原母体的Ｃ＿（２／ｃ）结构。交流阻抗技术测定的电导率数据显示含不同的二价替代离子的Ｎａｓｉｃｏｎ的电导率相差甚大。其中最好的是Ｍｇ￣（２＋）－Ｎａｓｉｃｏｎ，其电导率在４００℃时可达到１．４８×１０￣（－２）Ｓ／ｃｍ。Ｍｇ￣（２＋）－Ｎａｓｉｃｏｎ用作微功率固态电池Ｍｇ／ＣｕＣｌ的电解质，该电池的开路电压为２．０７Ｖ，短路电流为１ｍＡ。平均放电电压为１．６Ｖ，电池的放电容量是３．４ｍＡＨ。     

Ag—BaO纳米复合薄膜在红外超短激光脉冲作用下的内场助…

Ａｇ－ＢａＯ薄膜是一种新型光电发射薄膜材料。制备出ＩＴＯ／Ａｇ－ＢａＯ／ＡＵ三明治电极结构,在红外超短激光脉冲（ｈｖ＝１．１７ｅＶ）作用下,借助内场辅助方法,使得Ａｇ－ＢａＯ薄膜的光电发射量子效率提高了一个数量级,由钠场时的１０＾－７量级提高到内场偏压为１０Ｖ时遥２．２×１０＾－６量级;样品的阈值光强由６０ＫＷ／ｃｍ＾２降为４０ＫＷ／ｃｍ＾２,约降低了３０％。这些结果表明：内场辅助方法确实是降低Ａ     

三维碳化硅/碳化硅陶瓷基编织体复合材料

采用化学气相浸渗法（ＣＶＩ）,制备出三维Ｈｉ－ＮｉｃａｌｏｎＳｉＣ／ＳｉＣ陶瓷基编织体复合材料．经３０ｈ ＣＶＩ致密化处理后,复合材料的密度达到 ２５９·ｃｍ－３,所研制的三维 ＳｉＣ／ＳｉＣ复合材料不仅具有较高的强度,而且表现出优异的韧性和类似金属材料非灾难性的断裂特征．复合材料的主要力学性能指标为：弯曲强度 ８６０ＭＰａ,断裂位移 １．２ｍｍ,断裂韧性４１．５ＭＰａ·ｍ１／２,断裂功２８．１ｋＪ·ｍ－２,冲击韧性３６．０ｋＪ·ｍ－２．     

MPCVD法在Si衬底上生成β—C3N4晶态薄膜的研究

以Ｎ２,ＣＨ４作为反应气体,采用微波等离子体化学气相沉积法（ＭＰＣＶＤ）进行碳氮膜的合成研究。通过控制反应温度、气体流量、微波功率、反应气压,在Ｓｉ（１１１）和Ｓｉ（１００）基底上气相合成β－Ｃ３Ｎ４晶态薄膜。扫描电子显微镜（ＳＥＲＭ）下观察到生长在Ｓｉ基底上的薄膜具有六角晶棒的密结构。ＥＤＸ分析胡沉积条件的不同,六角晶棒中Ｎ／Ｃ在１．０～２．０之间。Ｘ射线衍射分析（ＸＲＤ）发现薄膜中含有β－Ｃ３     

SiC埋层结构与C^＋注入剂量关系

采用ＭｅｔａｌＶａｐｏｒＶａｃｕｕｍＡｒｃ（ＭＥＶＶＡ）离子源的离子束合成法，往Ｓｉ衬底注入剂量为３．０×１０＾１７～１．６×１０＾１８ｃｍ＾－２的Ｃ＾＋制成ＳｉＣ埋层，Ｃ＾＋离子束的引出能量为５０ｋｅＶ，光电子能谱和红外吸收谱表明ＳｉＣ埋层的结构特征明显地依赖于剂量，采用ＭＥＶＶＡ离子源可以平均衬底温度低于４００℃时得到含有立方结构的ＳｉＣ埋层。     

n型GaSb,InGaAsSb的MBE生长和特性研究

本文报导了非故意掺杂ＩｎＧａＡｓＳｂ本底浓度的降低和掺Ｔｅｎ型ＧａＳｂ和ＩｎＧａＡｓＳｂ的ＭＢＥ生长与特性的研究结果。结果表明，通过生长工艺的优化，ＧａＳｂ和ＩｎＧａＡｓＳｂ的背景空穴浓度可分别降至１．１×１０~（１６）ｃｍ~（－３）和４×１０~（１６）ｃｍ~（－３），室温空穴迁移率分别为９４０ｃｍ２／ｖ．ｓ和２６０ｃｍ~２／ｖ．ｓ。用Ｔｅ作ｎ型掺杂剂，可获得载流子浓度在１０~（１６）～１０~（１８）ｃｍ~（－３）的优质ＧａＳｂ和ＩｎＧａＡｓＳｂ外延层，所研制的材料已成功地制备出Ｄ_λ~＊＝４×１０~（１０）ｃｍＨｚ~（１／２）／Ｗ的室温ＩｎＧａＡｓＳｂ红外探测器和室温脉冲ＡｌＧａＡｓＳｂ／ＩｎＧａＡｓＳｂ双异质结激光器。     

PECVD法淀积氮化硼薄膜场发射特性研究

用 Ｂ２Ｈ６和 ＳｉＨ４作反应气体,通过射频等离子体增强化学气相淀积（ＲＦ－ＰＥＣＶＤ）方法,在 Ｓｉ（１００）面上沉积生长ＢＮ薄膜,用Ｓ－５２０扫描电子显微镜对所得薄膜进行观测,并用红外透射光谱测试分析了膜的成分。在室温、压力为 ８ × １０－４ Ｐａ条件下,对 ＢＮ薄膜的电流一电压特性进行测量,并得到了 Ｆｏｗｌｅｒ－Ｎｏｒｄｈｅｉｍ特性曲线,ＢＮ膜的场发射开启电场为９ Ｖ／μｍ,在电场３７．５ Ｖ／μｍ时,电流密度达到２４．８ ｍＡ／ｃｍ２。     

MAGNETIC PROPERTIES AND APPLICATIONS OF NEWLY-DEVELOPED NANOCRYSTALLINE Fe_(73.5)Cu_1Nb_2V_1Si_(13.5)B_9 ALLOY

报道了新开发的纳米晶Ｆｅ７３．５Ｃｕ１Ｎｂ２Ｖ１Ｓｉ１３．５Ｂ９合金的综合软磁性能。新合金的高频铁损水平为：Ｐ３／１００ｋ＝５１０ｋＷ·ｍ－３，Ｐ２／２００ｋ＝７４８ｋＷ·ｍ－３，Ｐ２／５００ｋ＝３６７１ｋＷ·ｍ－３和Ｐ０．５／１０００ｋ＝８７１ｋＷ·ｍ－３。新合金的铁损比早期开发的纳米晶Ｆｅ－Ｃｕ－Ｎｂ－Ｓｉ－Ｂ合金的低且明显低于优良的功率Ｍｎ－Ｚｎ铁氧体Ｈ７ｃ４的铁损。对铁损与频率和幅值磁通密度的关系进行了分析。也报道了新合金在若干方面的实际应用。     

δ－掺杂GaAs／AlxGa_（1－x）As二维电子气结构材料的GSMBE生长与特性

本文用ＧＳＭＢＥ技术生长纯度ＧａＡｓ和δ－掺杂ＧａＡｓ／Ａｌ_ｘＧａ_（１－ｘ）Ａｓ结构二维电子气材料并对其电学性能进行了研究。对于纯度ＧａＡｓ的ＧＳＭＢＥ生长和研究，在低掺Ｓｉ时，载流子浓度为２×１０~（１４）ｃｍ~（－３），７７Ｋ时的迁移率可达８４，０００ｃｍ~２／Ｖ．ｓ。对于用ＧＳＭＢＥ技术生长的δ－掺杂ＧａＡｓ／Ａｌ_ｘＧａ_（１－ｘ）Ａｓ二维电子气材料，在优化了材料结构和生长工艺后，得到了液氮温度和６Ｋ迁移率分别为１７３，５８３ｃｍ~２／Ｖ．５和７．６７×１０~５ｃｍ~２／Ｖ．ｓ的高质量ＧａＡｓ／Ａｌ_ｘＧａ_（１－ｘ）Ａｓ二维电子气材料。     

Deposition of GaN films on (1 1 1) Si substrates by alternate supply of TMG and NH3

GaN films were grown on (1 1 1) Si substrates at 1000 °C by separate admittances of trimethylgallium (TMG) and ammonia (NH₃). To achieve high quality GaN films, the optimization in growth temperature and layer thickness of AlN buffer layer between GaN film and Si substrate is required. Cross-sectional transmission electron microscopic observations of the GaN/(1 1 1)Si samples show a nearly parallel orientation relationship between the (0 0 0 1) planes of GaN film and the (1 1 1) planes of Si substrate. Room temperature photoluminescence spectra of high quality GaN films show a strong near band edge emission and a weak yellow luminescence. The achievement of high quality GaN films on (1 1 1) Si substrates is believed to be attributed to enhancement in surface mobilities of the adsorbed surface species and adequate accommodation of lattice mismatch between high temperature AlN buffer layer and Si substrate.     

Preparation of AlN thin films by nitridation of Al-coated Si substrate

AlN thin films have been grown on Al-coated Si(100) and Si(111) substrates by using nitridation in high-purity nitrogen ambient, where the Al layer was previously deposited on Si by ultra-high vacuum (UHV) electron beam evaporation. The temperature of nitridation was found to play an important role in the formation of AlN films. XRD results showed AlN films formed by nitridation at 1000°C for 30 min exhibited good crystallinity with the preferred orientation of (002) for both Si(111) and Si(100) cases. Other analysis techniques, like Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy have been used to evidence the formation and purity of the AlN films. Scanning electron microscope observations of the films revealed a closely-packed granular texture.     

Effect of substrate temperature and bias voltage on the crystallite orientation in RF magnetron sputtered AlN thin films

The crystal orientation and residual stress of AlN thin films were investigated using X-ray diffraction and substrate curvature method. The AlN films were deposited on Si(100) by RF magnetron sputtering in a mixed plasma of argon and nitrogen under various substrate negative bias V_s (up to − 100 V) and deposition temperature T_s up to 800 °C. The results show that lower temperature and moderate bias favor the formation of (002) plane parallel to the substrate surface. On the contrary, strong biasing beyond − 75 V and deposition temperature higher than 400 °C lead to the growth of (100) plane. At the same time nanoindentation hardness and compressive stress measured by substrate curvature method showed significant enhancement with substrate bias and temperature. The biased samples develop compressive stress while unbiased samples exhibit tensile or compressive stress depending on plasma power and temperature. The relationships between deposition conditions and crystallographic orientation of the films are discussed in terms of surface energy minimization and ion bombardment effects.     

Microstructure and optical properties of cubic AlN/TiN bilayers deposited by laser molecular beam epitaxy

AlN/TiN bilayers were deposited on Si(100) substrates with varying laser pulse energy by laser molecular beam epitaxy (LMBE) technique, and their growth mode, crystal structure and optical properties were investigated. The results indicated that atomically flat TiN single films and AlN/TiN bilayers with layer-by-layer growth mode were successfully grown on Si(100) substrates at optimal laser pulse energy. Both TiN and AlN in the grown bilayers exhibited the NaCl-type cubic structure with the same (200) preferred orientation, showing an excellent epitaxial relationship. TiN single film was more reflective in the infrared range and presented a small transparent window centered at wavelength of 404 nm. Reflectance spectrum of AlN film on top of TiN indicated the sharp absorption at about 246 nm, yielding a bandgap energy of 5.04 eV comparable to the theoretical calculation of bulk cubic AlN, but scarcely reported by the experimental data.     

A parametric study of AlN thin films grown by pulsed laser deposition

High quality AlN thin films were grown at 200–450°C on sapphire substrates by laser ablation of Al targets in nitrogen reactive atmosphere. The nitrogen pressure was varied between 10⁻³ and 10⁻¹ mbar. The reactive gas pressure during irradiation and the temperature of the substrate were found to essentially influence the quality of the layers. X-ray diffraction analysis evidenced the formation of highly orientated layers for a very restrictive set of parameters. Other analysis techniques, like X-ray photoelectron spectroscopy, secondary ion mass spectroscopy, optical transmission spectroscopy have been used to evidence the good stoichiometry and purity of the films. The characteristics of these films were compared with those of AlN thin films deposited in similar experimental conditions, on Si (100) and Si (111) substrates.     

Dielectric properties of AlN films prepared by laser-induced chemical vapour deposition

The dielectric properties and electrical conductivity of AlN films deposited by laser-induced chemical vapour deposition (LCVD) are studied for a range of growth conditions. The static dielectric constant is 8.0 ± 0.2 over the frequency range 10²−10⁷ Hz and breakdown electric fields better than 10⁶ V cm⁻¹ are found for all films grown at temperatures above 130°C. The resistivity of the films grown under optimum conditions (substrate temperature above 170°C, NH₃/TMA flow rate ratio greater than 300 and a deposition pressure of 1–2 Torr) is about 10¹⁴ Ω cm and two conduction mechanisms can be identified. At low fields, F < 5 × 10⁵ V cm⁻¹ and conductivity is ohmic with a temperature dependence showing a thermal activation energy of 50–100 meV, compatible with the presumed shallow donor-like states. At high fields, F > 1 × 10⁶ V cm⁻¹, a Poole-Frenkel (field-induced emission) process dominates, with electrons activated from traps at about 0.7–1.2 eV below the conduction band edge. A trap in this depth region is well-known in AlN. At fields between 4 and 7 × 10⁵ V cm⁻¹ both conduction paths contribute significantly. The degradation of properties under non-ideal growth conditions of low temperature or low precursor V/III ratio is described.     

Deposition and characterization of c-axis oriented aluminum nitride films by radio frequency magnetron sputtering without external substrate heating

Aluminum nitride (AlN) films were deposited on a variety of substrates (glass, Si, oxidized Si, Al-SiO₂-Si, Cr-SiO₂-Si, and Au-Cr-SiO₂-Si) by radio frequency (RF) magnetron sputtering using an AlN target. The films were deposited without external substrate heating. The effect of RF power, ambient gas (Ar and Ar-N₂) and sputtering pressure on deposition rate and crystallinity were investigated. The structure and morphology of the films were studied by X-ray diffraction, scanning electron microscopy and atomic force microscopy techniques. These investigations revealed that the AlN films prepared in mixed gas ambient (Ar-N₂) were highly c-axis oriented with moderate surface roughness on all the substrate. A strong IR absorption band was observed around 670 cm^− 1 which confirms the presence of Al-N bond in the film. The dc resistivity of the films was measured to be in the range of 10¹¹ to 10¹² Ω-cm at moderate electric fields. The application of these films in piezoelectric based micro-electro-mechanical systems is discussed.     

Synthesis and surface acoustic wave properties of AlN films deposited on LiNbO3 substrates

The c-axis-oriented aluminum nitride (AlN) films were deposited on z-cut lithium niobate (LiNbO₃) substrates by reactive RF magnetron sputtering. The crystalline orientation of the AlN film determined by x-ray diffraction (XRD) was found to be dependent on the deposition conditions such as substrate temperature, N₂ concentration, and sputtering pressure. Highly c-axis-oriented AlN films to fabricate the AlN/LiNbO₃-based surface acoustic wave (SAW) devices were obtained under a sputtering pressure of 3.5 mTorr, N₂ concentration of 60%, RF power of 165 W, and substrate temperature of 400°C. A dense pebble-like surface texture of c-axis-oriented AlN film was obtained by scanning electron microscopy (SEM). The phase velocity and the electromechanical coupling coefficient (K²) of SAW were measured to be about 4200 m/s and 1.5%, respectively. The temperature coefficient of frequency (TCF) of SAW was calculated to be about -66 ppm/°C     

Growth of highly c-axis oriented aluminum nitride thin films on β-tantalum bottom electrodes

We have investigated the influence of tantalum (Ta) bottom electrodes on the crystallinity and crystal orientation of aluminum nitride (AlN) thin films. AlN thin films and Ta electrodes were prepared by using rf magnetron sputtering method. The crystal structure of the Ta electrodes was tetragonal (β-Ta, a metastable phase) at room temperature. The crystallinity and orientation of the AlN thin films and Ta electrodes strongly depended on sputtering conditions. Especially, the crystallinity and crystal orientation of the Ta electrodes were influenced by their film thickness and the substrate temperature. When the thickness of the Ta bottom electrodes was 200 nm and the substrate temperature was 100 °C, the AlN thin films indicated high c-axis orientation (the full width at half maximum of rocking curve of 3.9°). The crystal orientation of the AlN film was comparable to that of AlN thin films deposited on face centered cubic (fcc) lattice structure metal, such as Au, Pt and Al, bottom electrodes.     

Polycrystalline AlN films with preferential orientation by plasma enhanced chemical vapor deposition

AlN thin films for acoustic wave devices were prepared by Microwave Plasma Enhanced Chemical Vapor Deposition under different process conditions, employing Si (100) and Pt (111)/SiO₂/Si (100) substrates. The films were characterized by X-ray diffraction, Fourier transform infrared transmission spectroscopy, atomic force microscopy, scanning electron microscopy, and transmission electron microscopy. The values of the distance between the plasma and the tri-methyl-aluminum precursor injector, the radiofrequency bias potential, and the substrate temperature were central in the development of polycrystalline films. The choice of the chamber total pressure during deposition allowed for the development of two different crystallographic orientations, i.e., <0001> or <1010>. The film microstructures exhibited in general a column-like growth with rounded tops, an average grain size of about 40 nm, and a surface roughness lower than 20 nm under the best conditions.