超薄四面体非晶碳膜的结构和性能

使用磁过滤阴极真空电弧(FCVA)技术制备不同厚度的超薄四面体非晶碳膜(ta-C)，研究了表征和测量超薄ta-C碳膜微观结构和性能的方法以及膜厚的影响。使用X射线衍射仪验证椭圆偏振光谱仪联用分光光度计表征膜厚度的可靠性并测量了膜密度；用拉曼谱分析薄膜的内在结构，验证用椭偏联用分光光度计表征sp³ C含量的可靠性；用Stoney^，s公式计算了薄膜的残余应力。结果表明，薄膜的厚度由7.6 nm增大到33.0 nm其沉积速率变化不大，为1.7±0.1 nm/min；根据椭偏联用分光光度计的表征结果，薄膜中sp³ C的含量逐渐减少，拓扑无序度降低，与拉曼谱的表征结果一致；厚度为7.6 nm的超薄ta-C碳膜中p³ C的含量最高；随着厚度的增大薄膜中的残余压应力从14 GPa降低到5 GPa；厚度为11.0 nm的薄膜主体层密度最大，为3070 kg/m³，致密性较好；厚度对薄ta-C碳膜表面粗糙度的影响较小。用椭偏和分光光度计测量超薄ta-C碳膜的厚度和表征显微结构是可行的，X射线反射法可用于测量超薄ta-C碳膜密度和表面粗糙度，但是对薄膜的质量要求较高。     

电弧离子镀CrAlN-DLC硬质复合薄膜的成分、结构与性能

为了改善CrAlN薄膜的摩擦性能, 本研究在增强磁过滤脉冲偏压电弧离子镀设备上, 用分离靶弧流调控技术在硬质合金基体上分别制备了不同成分的CrAlN-DLC硬质复合薄膜, 并采用不同手段表征了薄膜的表面形貌、成分、相结构以及力学和摩擦性能。结果表明, 不同成分薄膜表面均平整致密, 膜厚均在1.05 μm左右。随着靶弧流比I_C/I_CrAl的升高, 薄膜中碳的原子分数由33.1%升至74.6%。薄膜的相结构主要由晶体相和非晶相复合组成, 其晶体相主要为c-(Cr,Al)N相, 且随着碳含量增大晶体相减少、晶粒尺寸减小, 其非晶相主要为DLC, 其中sp²/sp³的比值随碳含量增大而减小。相应地, 薄膜的硬度随着碳含量增大而提高, 当碳的原子分数为74.6%时, 达到最大值(26.2±1.4) GPa, 且该成分点处薄膜摩擦系数也降至最小值0.107, 磨损率仅为3.3×10^-9 mm³/Nm。综合而言, 当非晶DLC相最多时, CrAlN-DLC复合薄膜的综合性能达到最佳, 较之CrAlN薄膜, 摩擦性能显著提高。     

金属过渡层类型对非晶碳膜结构性能的影响

采用直流磁控溅射技术制备不同金属过渡层(Cr, Ti, W)的类石墨非晶碳膜(GLC), 研究过渡层类型对非晶碳膜微结构的影响, 并考察其在人工海水中摩擦性能的变化。研究结果表明: Cr/GLC薄膜sp²杂化键含量最高, 沿GLC表面到铬碳界面方向, sp²杂化键含量逐渐增大, Ti过渡层和W过渡层的sp²杂化键含量变化不明显。Cr/GLC薄膜较高的sp²杂化键含量有助于其在摩擦过程中产生可以充当润滑相的石墨化转化摩擦转移膜。在三种涂层中, Cr/GLC薄膜表现出最高的腐蚀电位-0.16 V和最低的腐蚀电流密度4.42×10^-9 A/cm²。因此相较于Ti, W作过渡层的GLC薄膜, Cr/GLC薄膜在海水环境下表现出优异的摩擦学特性。     

厚度对真空电弧制备传感器用非晶ta-C膜性能的影响

采用双弯曲磁过滤阴极真空电弧沉积方法在传感器用P型单晶硅上制备ta-C膜,并通过实验测试的手段研究厚度对其组织及性能的影响。研究结果表明:逐渐延长沉积时间后,沉积速率始终保持1.6 nm/min的稳定状态。分别运用椭偏仪和光度计测定ta-C膜的厚度结果基本一致,差值小于2 nm。随着膜厚的增加,sp³C比例发生了减小,原先的sp³结构逐渐转变为sp²结构。当膜厚增大后,ta-C膜内形成了更高比例的sp³C。当膜厚增大后,G峰发生了低位移动,此时膜内的sp³C比例发生了降低。当膜厚增大后,ta-C膜色散值和残余压应力发生了不断减小,表明膜获得了更小的拓扑无序度。不同厚度的涂层粗糙度基本接近,都在0.6 nm以内。膜表面呈现光滑的连续分布形态,粗糙度保持基本恒定。     

具有梯度渐变折射率的超疏水减反膜的制备及其性能

具有梯度折射率的减反膜可以在更宽光谱波段和更大入射光角度实现减反射性能。本研究利用溶胶-凝胶和溶剂热法分别合成实心氧化硅(SiO₂)、空心氧化硅(H-SiO₂)和空心氟化镁(MgF₂)溶胶, 利用浸渍-提拉法在玻璃双面镀制SiO₂/H-SiO₂/MgF₂梯度折射率薄膜。结果表明, 在380~1600 nm波长, 镀膜基片在光垂直入射时透光率高达99.88%, 当光以0°~45°入射时, 平均透光率均高于97.85%, 即使光以75°入射时, 最高透光率仍达95.51%。同时发现, 经十六烷基三甲氧基硅烷(HDTMOS)修饰, 薄膜疏水角达到150.6°, 显示出良好的疏水自清洁效果。     

沉积时间对聚醚醚酮表面类金刚石薄膜的结构和性能的影响

采用直流磁控溅射技术在聚醚醚酮(PEEK)表面制备不同厚度的类金刚石(DLC)薄膜,研究了沉积时间对其表/界面结构、组分、疏水、力学和光透过性能的影响。结果表明,在平均沉积速率为5.71 nm/min的条件下,随着沉积时间的延长DLC薄膜的厚度线性增大、碳原子的致密性提高、界面互锁结构增强,而界面结合强度逐渐降低。沉积时间≤15 min时,基体结构的影响使拟合计算出的I_D/I_G值为0.23~0.25和sp²/sp³比值较小(0.58~0.74);沉积时间>15 min时基体的影响较小,I_D/I_G值突增大至0.81,sp²/sp³值也比较大(0.96~1.12)。沉积时间的延长使PEEK基体的温度逐渐升高,使膜内的sp²/sp³值逐渐增大。薄膜表面的氧含量先降低然后趋于平缓,部分C=O转化为C-O。随着沉积时间的延长,PEEK/DLC复合薄膜的硬度、弹性模量及防紫外线和阻隔红外线性能都逐渐提高,其表面粗糙度和疏水性的变化趋势是先提高后降低。沉积时间为32 min的薄膜,其表面粗糙度和水接触角达到最大值,分别为495 nm和108.29°。     

掺铋钇铁石榴石磁光陶瓷的热压烧结及其性能研究

钇铁石榴石(Y₃Fe₅O₁₂, YIG)材料因其优异的磁性能和磁光性能在微波通信、激光技术和光纤通讯等领域具有重要应用。离子掺杂是提高YIG材料磁光性能的有效途径之一, 本研究选择离子半径适配的Bi³⁺掺杂改性YIG陶瓷以提高材料的磁光性能。本工作采用固相法热压烧结制备Bi_xY_3-xFe₅O₁₂ (x=0、0.3、0.6、0.9)陶瓷, 并研究Bi³⁺掺杂对YIG陶瓷材料相结构、微观形貌、红外透过性、磁性能以及磁光性能的影响。结果表明: 陶瓷样品均呈石榴石立方相结构; 显微结构致密, Bi³⁺掺杂后晶粒尺寸不同程度增大; 样品红外透过率良好, 随Bi³⁺掺杂量增大而降低; 陶瓷样品的法拉第旋转角随Bi³⁺掺杂量增加呈线性变化, Bi³⁺掺杂量每增加1% (原子分数), 在波长1064 nm和1550 nm处变化量分别约为-49.0 (°)/cm和-30.2 (°)/cm。Bi_0.6Y_2.4Fe₅O₁₂陶瓷样品在1064 nm和1550 nm波长下法拉第旋转角分别达到-703.3 (°)/cm和-461.5 (°)/cm, 绝对值远高于未掺杂YIG陶瓷的277.6 (°)/cm和172.0 (°)/cm。由此可见, 掺杂适量Bi³⁺可以显著增强YIG陶瓷材料的磁光性能。     

氧化铈空心球可控合成及其对Pt基催化剂电催化性能的影响

采用水热合成法, 以碳球为模板, 改变焙烧升温速率, 控制影响铈物种的扩散、渗透及碳球结构的收缩率, 制备了单、双壳层CeO₂空心球。通过微波辅助乙二醇还原氯铂酸法制备了Pt-CeO₂/RGO催化剂, 研究了CeO₂空心球的添加对Pt基催化剂电催化性能的影响。利用X射线衍射仪(XRD)、比表面积及孔径分析仪(BET)、扫描电镜(SEM)和电子能谱(EDAX)、透射电镜(TEM)、X射线光电子能谱(XPS)对CeO₂及催化剂的微观结构进行了表征, 利用电化学工作站对催化剂进行电化学性能测试。结果表明: 单、双壳层CeO₂空心球的比表面积为124.44 m²/g、140.95 m²/g, 孔容为0.014427 cm³/(g·nm)、0.018605 cm³/(g·nm), 孔径分布在2~4 nm范围内。催化剂中的CeO₂保持原有的球状形貌, Pt纳米粒子主要分布在CeO₂附近; 当RGO∶CeO₂=1∶2时, 添加了双壳层CeO₂空心球的Pt-CeO₂/RGO催化剂的电催化性能最优, 电化学活性表面积为94.27 m²/g, 对乙醇氧化的峰电流密度值为613.54 A/g, 1000 s的稳态电流密度值为135.45 A/g。     

硅片上集成高介电调谐率的柱状纳米晶BaTiO3铁电薄膜

钛酸钡(BaTiO₃)具有优异的介电、铁电、压电和热释电等性能, 在微电子机械系统和集成电路领域具有广泛的应用。降低BaTiO₃薄膜的制备温度使其与现有的CMOS-Si工艺兼容, 已成为应用研究和技术开发中亟需解决的问题。本研究引入与BaTiO₃晶格常数相匹配的LaNiO₃作为缓冲层, 以调控其薄膜结晶取向, 在单晶Si(100)基底上450 ℃溅射制备了结构致密的柱状纳米晶BaTiO₃薄膜。研究表明：450 ℃溅射温度在保持连续柱状晶结构和(001)择优取向的前提下, 能获得相对较大的柱状晶粒(平均晶粒直径27 nm), 一定残余应变也有助于其获得了较好的铁电和介电性能。剩余极化强度和最大极化强度分别达到了7和43 μC·cm^-2。该薄膜具有良好的绝缘性, 在 0.8 MV·cm^-1电场下, 漏电流密度仅为10^-5 A·cm^-2。其相对介电常数ε_r展现了优异的频率稳定性：在1 kHz时ε_r为155, 当测试频率升至1 MHz, ε_r仅轻微降低至145。薄膜的介电损耗较小, 约为0.01~0.03 (1 kHz ~ 1 MHz)。通过电容-电压测试, 该薄膜材料展示出高达51%的介电调谐率, 品质因子亦达到17(@1 MHz)。本研究所获得的BaTiO₃薄膜在介电调谐器件中有着良好的应用前景。     

铜膜碘化法制备p型CuI薄膜及其用作空穴传输层的反型钙钛矿电池性能

γ相碘化亚铜(γ-CuI)是一种带隙为3.1 eV的p型半导体材料, 适合应用于发光二极管和太阳能电池等光电子器件。本研究利用简单的铜膜碘化法制备了CuI薄膜, 探究了碘化时间、温度及铜/碘比等生长条件对其透明导电性能的影响。在最优碘化时间(30 min)和碘化温度(120℃)下, 制备出了高透过率(可见光范围>75%)、导电性能好(电阻率4.4×10^-2 Ω·cm)的CuI薄膜。利用CuI薄膜作为空穴传输层, 组装了CuI/CH₃NH₃PbI₃/PCBM反型平面钙钛矿电池, 获得的最高光电转换效率为8.35%, 讨论了CuI薄膜透明导电性能对钙钛矿电池光电转换效率的影响机理。     

A theory for the formation of tetrahedral amorphous carbon including deposition rate effects

A theoretical model is presented to describe the effect of ion beam bombardment rate on the formation of tetrahedral amorphous carbon (ta-C) films. The critical ion energy, E_c, corresponding to a 50% sp³ content in the films, is found to be dependent on both the effective thermal resistance and the ion beam bombardment rate. In the model, the ‘window’ width in the ion energy scale for the formation of ta-C material increases with decreasing deposition rate and with a reduction in the effective thermal resistance, until limited by lower and upper boundary thresholds. Experimental data are reproduced by the model. The plasmon energy, which correlates with sp³ fraction, is found experimentally of be higher for lower deposition rate and smaller effective thermal resistance. Data points for high sp³ content ta-C films deposited on silicon substrates at room temperature occupy a region in the ion energy-deposition rate (E-r) diagram similar to that predicated from the theory.     

Electrical properties of reactively sputtered carbon nitride films

Carbon nitride films with β-C₃N₄ crystals of 200 nm grain size were grown on Si (1 0 0) substrates using magnetron sputtering. These films were characterized by transmission electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Carbon nitride films had low surface roughness. Maximum N/C ratio of 0.5 was achieved in the films. Chemical bonds of sp, sp² and sp³ coexisted in the films. The fraction of each bond was related to the deposition conditions. The resistivities of the films were measured, which ranged from 1×10³ to 1×10⁷ Ω cm. The measured resistivity results indicated that the carbon nitride films had semiconductive properties. The resistivity largely depended on the sp³/sp² ratio. Effects of N₂ fraction, target current and substrate bias were investigated. All these deposition parameters had influence on the chemical bonds of the films, and on the resistivities too. High sp³/sp² ratio resulted in high resistivity.     

Characterization of ion-beam-deposited diamond-like carbon films

Diamond-like carbon (DLC) films are excellent prospects for a wide range of high-technology applications but their precise structure and properties are not well understood. The purpose of the present work was to use several complementary techniques to characterize the nature, structure and microstructure of DLC films. Thin DLC films were deposited on various substrates in the presence of a Si interlayer (500 Å thick) using CH₄ ion-beam deposition at an acceleration energy of 750 eV and a current density of about 2.5 mA cm⁻². The Si interlayer was deposited by either e-beam evaporation or Si evaporation enhanced by Ar⁺ beam bombardment (1 keV). The produced DLC films were featureless, very smooth and of high hardness (2900–3300 kg mm⁻²). Auger electron spectroscopy and electron diffraction showed that the films were mainly amorphous. Their microstracture was characterized by a three-dimensional network structure with a medium-range order of about 25 nm. Fourier transform infrared and Raman spectroscopies showed that the films were mainly composed of sp³ and sp² carbon-bonded hydrogen. The sp³/sp² ratio varied from 3.2 to 4.1 and was found to depend on the nature of the Si bond layer. The results showed that the nucleation of the diamondlike structure was promoted on the Si interlayer that was deposited under Ar⁺ beam bombardment. This effect can be explained by the higher surface roughness produced in this interlayer as suggested by the reflectivity measurements. Spectroscopic ellipsometry revealed that the films had an optical band gap between 1.56–1.64 eV. The present results are consistent with previous proposals suggesting that the DLC structure is composed of small graphitelike clusters (involving fused six-fold rings) that are interconnected by sp³-bonded carbon.     

Low temperature internal friction of diamond-like carbon films

We have studied the internal friction of amorphous diamond-like carbon films prepared by pulsed-laser deposition from 0.4 to 300 K. The low temperature internal friction below 10 K is dominated by the atomic tunneling states for amorphous solids, which is a measure of structure disorder. We have tried to vary the content of sp³ carbon atoms versus sp² ones by changing laser fleunce, by doping with N and Ar, and by annealing at 500 °C for 20 min. Our results show that the internal friction varies about one order of magnitude from 2×10⁻⁵ to 2×10⁻⁴, and its value is higher with higher sp³ content when the film quality is generally considered superior. However, it is known that as-deposited diamond-like carbon films with high sp³ content are heavily stressed. Annealing and doping are used to release the stress. We conclude that in addition to tetrahedral bonding, low stress is also important in reducing structure disorder associated with the low energy tunneling states in amorphous solids.     

Implantation effect of diamond-like carbon films by 110 keV nitrogen ions

Diamond-like carbon films, grown on microscope slides by a dual-ion beam sputtering system, were implanted by 110 keV N⁺ under the doses of 1 × 10¹⁵, 1 × 10¹⁶ and 1 × 10¹⁷ions cm⁻² respectively. The implantation induced changes in electrical resistivity of the films and in infrared (IR) transmittance of the specimens were investigated as a function of implantation dose. The structural changes of the films were also studied using IR spectroscopy and Raman spectroscopy. It was observed that, with the increase of implantation dose, the diamond-like carbon films display two different stages in electrical and optical behaviours. The first is the increase of both the film resistivity and the IR transmittance of specimen at the dose of 1 × 10¹⁵ ions cm⁻² which, we consider, is attributed to the implantation-induced increase sp³ C---H bonds. However, when the doses are higher than 1 × 10¹⁵ ions cm⁻², the film resistivity and the IR transmittance of specimen decrea significantly and the decrease rates at dose range of 1×10¹⁶ to 1×10¹⁷ ions cm⁻² are smaller than those between 1×10¹⁵ and 1 × 10¹⁶ ions cm⁻². We conclude that the significant reductions of the two parameters at high doses are caused by the decreases of bond-angle disorder and of sp³ C---H bonds, the increases of sp² C---C bonds dominated the crystallite size and/or number and also the sp² C---H bonds. The smaller decrease rates at a dose range of 1 × 10¹⁶ to 1 × 10¹⁷ ions cm⁻² may be caused by further recombination of some retained hydrogen atoms to carbon atoms.     

紫外光辐照下钛硅共掺杂类金刚石薄膜微结构的演化

采用中频磁控溅射Ti80Si20合金靶在单晶硅表面制备了钛硅共掺杂的类金刚石薄膜。利用紫外-可见光多波长Raman光谱表征薄膜微结构, 并结合FTIR光谱研究了紫外光辐照对类金刚石薄膜微结构的影响, 进一步讨论了紫外光辐照下薄膜微结构的演化机理。结果表明: 非晶结构的类金刚石薄膜出现反式聚乙炔和聚对苯乙炔类聚合物结构以及sp杂化的线型卡宾碳结构。紫外光辐照诱导薄膜微结构驰豫和重构, 薄膜Si-O和C-O键含量增加, C=C和C-H键含量减少; 同时薄膜sp²团簇尺寸减小而无序度增大。