聚乙烯醇改性对原子层沉积氧化铝复合隔膜的影响

原子层沉积技术(ALD)是一种具有表面自限性反应的薄膜生长技术,可以精准控制薄膜的生长。本文研究了ALD技术包覆聚烯烃隔膜,制作纳米氧化铝聚烯烃复合隔膜。聚烯烃膜表面无ALD氧化铝反应基团,造成ALD氧化铝生长成核慢,前期反应效率低,最终生长的氧化铝多形成团簇而非完整覆盖的薄膜。为了增强ALD氧化铝包覆聚乙烯膜(PE)的全覆盖薄膜生长,将PE膜进行了聚乙烯醇(PVA)表面改性处理,然后进行ALD Al_2O_3生长。通过扫描电镜、红外光谱、电感耦合发射光谱仪等技术手段系统分析了PVA表面改性对ALD Al_2O_3包覆PE膜性能指标的影响。结果表明,PVA改性可以简单有效地在PE膜上增加羟基(-OH)作为ALD反应位点。处理后的PE膜进行ALD Al_2O_3生长,前驱体进入反应腔室后更易与表面羟基进行反应,提高表面生长效率,纤维上均匀包覆氧化铝,无岛状生长的Al_2O_3团簇。同时PVA改性可以增强复合膜的耐热收缩性能,减少厚度增加,减轻机械结构的损坏。     

原子层沉积氧化铝包覆羰基铁粉的抗腐蚀性及吸波性能

为了提高羰基铁粉的抗腐蚀能力及改善其电磁性能, 以TMA和H₂O为前驱体, 利用原子层沉积(ALD)方法对羰基铁粉进行表面包覆改性, 在羰基铁粉表面包覆不同厚度的氧化铝。通过扫描电镜(SEM)、透射电镜(TEM)、综合热分析仪(TGA)、红外光谱(FTIR)和矢量网络分析仪等技术手段系统分析了改性前后羰基铁粉性能指标。结果表明, 通过ALD方法可在羰基铁粉表面生长纳米级别具有良好保型的氧化铝薄膜, 形成了极佳的羰基铁/氧化铝壳层结构复合材料。与原样品相比, 包覆改性后的羰基铁粉热稳定性与抗腐蚀性有极大的提高, 且随着包覆厚度的增加, 抗氧化能力增强, 最大抗氧化温度可超过550℃。同时羰基铁粉包覆氧化铝后, 其介电常数明显减小, 磁导率变化相对较小, 改善了原羰基铁粉的电磁参数与吸波性能。     

Cu电极保护膜层氧化铝的原子层沉积工艺研究

介绍了硅功率器件Cu电极保护钝化膜层氧化铝的制备方法。采用热法ALD工艺和等离子增强ALD工艺在铜上沉积氧化铝薄膜,研究了不同ALD工艺、氧化剂种类、沉积温度和载气对氧化铝膜层质量及铜抗氧化保护效果的影响。结果表明：氧化剂对原子层沉积氧化铝薄膜的质量和铜电极的保护性能起着决定性作用;以臭氧(O₃)作为氧化剂,氧化铝薄膜极易脱落,与铜表面的结合力很差;以氧等离子体(O-)作为氧化剂,铜表面被氧化形成了氧化铜(CuO_x)层;而以水蒸气(H₂O)作为氧化剂,在低温100℃下,得到的Al₂O₃薄膜致密,无明显缺陷,且与铜金属层的结合力较优,对铜抗氧化保护效果良好;当沉积温度高于200℃时,原子层沉积氧化铝薄膜的缺陷明显增多;等离子增强ALD工艺中,当载气为Ar时,所得氧化铝膜厚度不均匀,铜电极发生强烈氧化。     

不同温度对原子层沉积掺铝氧化锌薄膜性能的影响

采用热原子层沉积(ALD)方法,在固定氧化锌与氧化铝沉积比例的情况下,研究了不同温度下在玻璃衬底上沉积的掺铝氧化锌薄膜性能的变化,特别是"ALD窗口"温度的影响。通过计算薄膜沉积速率,得到了薄膜沉积的"ALD窗口"温度范围为225~275℃,相应的沉积速率为0.214 nm/cycle。分析样品的表面形貌后发现,虽然反应的温度有所不同,但薄膜的微观结构均为密集堆积的纺缍体,它们的尺寸受到温度、晶体结构等因素的影响。结构分析表明,在"ALD窗口"温度范围内,所有沉积得到的样品均为(100)择优取向,并且结晶质量、晶粒尺寸以及(002)峰的相对强度均随着温度升高而增大。薄膜的光学透过率以及光学带隙没有随温度变化而表现出明显的变化,分别在80%(350~770 nm)和3.90 e V左右。薄膜的电导率和光学质量在"ALD窗口"内随温度增加而增长,直到300℃时达到最佳。     

等离子体辅助原子层沉积技术包覆硅基氮化物荧光粉的结果性能研究

采用等离子体辅助原子层沉积的方法,通过振动流化床,在硅基氮化物荧光粉表面保形地包覆了氧化铝薄膜。分别用傅立叶红外光谱(FTIR)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和pH计对包覆前后荧光粉的表面成分、形貌和耐水性进行了测试。最后,还用荧光光谱仪对包覆前后荧光粉的PL发光进行了表征。结果表明,氧化铝被保形地包覆在荧光粉颗粒表面。包覆大大提升了荧光粉在水中的稳定性。包覆一定厚度的氧化铝对发光性能有所提升并可以略微降低荧光粉的色温。     

锂电池中高比表面积的导电剂分散和ALD包覆性能优化

本研究以高比表面积的导电添加剂为基体材料,通过原子层沉积(ALD)法生长氧化铝纳米薄膜,制备改性高比表面积的导电添加剂。采用扫描电镜及透射电镜对包覆改性前后导电剂的形貌进行表征,发现采用ALD方法可以在高比表面积的导电添加剂表面生长纳米氧化铝。利用扣电方法测试改性导电剂对锂离子电池性能的影响。在高电压下,改性高比表面积的导电剂制备的锂离子电池在倍率循环性能、库伦效率、充放电性能等方面都有很大程度的提高。ALD氧化铝薄膜的厚度会影响锂离子电池性能。高比表面积的导电剂则需要更长时间的ALD生长氧化铝,达到提高锂离子电池倍率(0~8C)循环性能的结果。     

原子层沉积Al2O3薄膜钝化n型单晶硅表面的研究

以三甲基铝(TMA)和水为反应源,采用原子层沉积(ALD)技术在n型单晶硅表面沉积15nm、30nm和100nm的Al2O3薄膜,并对样品进行快速退火(RTA)处理。采用少子寿命测试仪测试样品的有效少子寿命,获得了表面复合速率(SRV),通过X射线光电子能谱(XPS)分析了薄膜的化学成分,在此基础上研究了薄膜厚度及退火条件对钝化效果的影响,并分析了钝化机理。结果表明:ALD技术制备的Al2O3薄膜经退火后可使n型单晶硅SRV值降低到7cm/s,表面钝化效果显著。     

硅片表面原子层沉积Al_2O_3薄膜及其长期腐蚀行为

目前,对硅基材表面利用原子层沉积技术(ALD)制备的Al_2O_3薄膜的耐蚀性鲜见研究报道。利用ALD技术在硅片表面制备非晶Al_2O_3薄膜。采用扫描电镜(SEM)观察薄膜的表面及截面形貌;采用X射线光电子能谱仪(XPS)分析薄膜的价键结构;通过交流阻抗谱和动电位极化曲线研究硅基材与薄膜在不同浸泡时间下的耐腐蚀性能;采用光学显微镜观察腐蚀过程中基材与薄膜的表面形貌。结果表明:ALD非晶态Al_2O_3薄膜具有致密结构,在浸泡过程中,镀膜基材比裸基材具有更好的耐腐蚀性能;且在长期浸泡情况下,Al_2O_3薄膜对基材仍能起到良好的保护作用。     

工艺气体比例对微波MOCVD沉积氧化铝膜性能影响

AlO薄膜作为高效太阳能电池中P层钝化薄膜引起了光伏龙头企业的关注。本文利用自主研发的线性微波等离子增强化学气相沉积系统(LMW-MOCVD)在单晶硅基体上用不同N_2O和TMA特气比例制备氧化铝膜层样品,并通过SEM、SE800椭偏仪对薄膜的成分、表面形貌、厚度、沉积速度、折射率测试分析。实验结果表明,随着N_2O比例增大,薄膜中O/Al原子比例有上升趋势;膜层沉积速度显著降低;膜层折射率开始趋于稳定而后迅速降低。所以,工艺气体比例对LMW-MOCVD沉积氧化铝膜的性能有明显影响。     

大气压介质阻挡放电等离子体辅助原子层沉积氧化铝阻隔膜

为了研究纳米氧化铝对双向拉伸聚对苯二甲酸乙二醇酯薄膜(BOPET)阻隔性能的影响,利用自行设计加工的大气压介质阻挡放电(DBD)等离子辅助原子层沉积(PAALD)设备,使用三甲基铝(TMA)和氧气等离子体(O²)在厚度为120 μm的BOPET上生长氧化铝(Al₂O₃)无机层。采用椭圆偏振仪、原子力显微镜、红外光谱仪、X射线光电子能谱分析和透湿仪等分别对氧化铝薄膜的厚度、表面形貌、成分和水蒸气透过率等进行测量和表征。结果表明,大气压DBD等离子体辅助沉积 Al₂O₃薄膜具有ALD生长特性,生长速率为0.27 nm/周期,高于在低压下由等离子体辅助ALD沉积的Al₂O₃的生长速率;生长的氧化铝薄膜结构致密、表面粗糙度小,薄膜成分较纯;其水蒸气透过率(WVTR)由PET原膜的3.17 g/(m²·d)低至0.05 g/(m²·d)。     

Conformal nanocoating of zirconia nanoparticles by atomic layer deposition in a fluidized bed reactor

Primary zirconia nanoparticles were conformally coated with alumina ultrathin films using atomic layer deposition (ALD) in a fluidized bed reactor. Alternating doses of trimethylaluminium and water vapour were performed to deposit Al(2)O(3) nanolayers on the surface of 26?nm zirconia nanoparticles. Transmission Fourier transform infrared spectroscopy was performed ex situ. Bulk Al(2)O(3) vibrational modes were observed for coated particles after 50 and 70?cycles. Coated nanoparticles were also examined with transmission electron microscopy, high-resolution field emission scanning electron microscopy and energy dispersive spectroscopy. Analysis revealed highly conformal and uniform alumina nanofilms throughout the surface of zirconia nanoparticles. The particle size distribution and surface area of the nanoparticles are not affected by the coating process. Primary nanoparticles are coated individually despite their high aggregation tendency during fluidization. The dynamic aggregation behaviour of zirconia nanoparticles in the fluidized bed plays a key role in the individual coating of nanoparticles.     

Explanation for the appearance of alumina nanoparticles in a cold wall Atomic Layer Deposition system and their characterization

An explanation for the possible mechanism of formation of alumina nanoparticles in Atomic Layer Deposition process of Alumina using Trimethyl aluminum (TMA) and water in a cold wall ALD chamber is given based on the physisorption of TMA and surface energy of alumina thin films. The sorption mechanism proposed is physisorption at the cold walls rather than the conventional chemisorption at the hot substrates as in the case of typical ALD. It is argued that when the surface energy of alumina is larger than the physorption energy, the newly forming film will try to reduce the surface area and assume spherical shape forming nano particles. Synthesized particles were characterized using XRD, SEM, HRTEM, SAED, FTIR and EDS. It was found that the particle size varied from ∼20 nm to 45 nm. The samples were identified as slightly aluminum rich alumina. The as prepared samples were amorphous whereas annealing at 1200 deg C made them crystalline. Dielectric studies of pelletized samples yielded a dielectric constant of 9.08 which agreed well with reported values.     

Admicellar polymerization of styrene with divinyl benzene on alumina particles: the synthesis of white reinforcing fillers

Admicellar polymerization has been used to form polymer coated white mineral particulates as alternatives to carbon black for application in rubber reinforcement. An ultra thin film of polystyrene and cross-linked with divinylbenzene was used to coat alumina particles. Optimization of reaction conditions was carried out, through investigation of factors that affect the adsorption of the surfactant, sodium dodecyl sulfate, on alumina and film formation. The surface modified particles were characterized using ultraviolet absorbance, thermogravimetry, scanning electron microscopy, and changes in hydrophobicity were determined qualitatively using a drop test. Results showed that alumina particles were successfully coated with poly(styrene-co-divinylbenzene), and their resistance to wetting by water was greatly enhanced after admicellar polymerization treatment.Shuqin Wang is an International visiting scholar from China to The University of Melbourne.     

Preparation of regularly structured nanotubular TiO2 thin films on ITO and their modification with thin ALD-grown layers

Nanotubular titanium dioxide thin films were prepared by anodization of titanium metal films evaporated on indium tin oxide (ITO) coated glass. A facile method to enhance the adhesion of the titanium film to the ITO glass was developed. An optimum thickness of 550 nm for the evaporated titanium was found to keep the film adhered to ITO during the anodization. The films were further modified by growing amorphous titania, alumina and tantala thin films conformally in the nanotubes by atomic layer deposition (ALD). The optical, electrical and physical properties of the different structures were compared. It was shown that even 5 nm thin layers can modify the properties of the nanotubular titanium dioxide films.     

Significant Capacity and Cycle‐Life Improvement of Lithium‐Ion Batteries through Ultrathin Conductive Film Stabilized Cathode Particles

Atomic layer deposition (ALD), as a thin film deposition technique, has been explored as a viable path to improve the performance of lithium‐ion batteries. However, a trade‐off between the species transport (capacity) and protection (lifetime), resulting from the insulating properties of ALD films, is the key challenge in ALD technology. Here we report a breakthrough to overcome this trade‐off by coating an ultrathin conformal cerium dioxide (CeO₂) film on the surfaces of LiMn₂O₄ particles. The optimized CeO₂ film (≈3 nm) coated particles exhibit a significant improvement in capacity and cycling performance compared to uncoated (UC), Al₂O₃ coated, and ZrO₂ coated samples at room temperature and 55 °C for long cycling numbers. The initial capacity of the 3 nm CeO₂‐coated sample shows 24% increment compared to the capacity of the uncoated one, and 96% and 95% of the initial capacity is retained after 1000 cycles with 1C rate at room temperature and 55 °C, respectively. The detailed electrochemical data reveal that the suppression of the impedance rise and the facile transport of the species are the main contributors to the success.     

Induction of hydroxycarbonate apatite formation on polyethylene or alumina substrates by spherical vaterite particles deposition

Hydroxycarbonate apatite (HCA) layers were formed on polyethylene (PE) or alumina substrates by depositing spherical sub-micron vaterite particles and then immersing in simulated body fluid (SBF). HCA formation on vaterite‐coated PE was faster than that on coated alumina (3 days for PE and 7 days for alumina). The adsorption of phosphate ions on the vaterite particles in SBF was studied by monitoring changes in the concentration of phosphorous in SBF and the surface charges of vaterite during the SBF immersion. The phosphorous concentration of SBF in which a vaterite-coated PE was immersed for 1 h was lower than that in which a vaterite-coated alumina was immersed. Zeta potential of the vaterite surface deposited on PE drastically decreased after 1 h immersion in SBF. The vaterite particles deposited on each substrate immediately adsorbed phosphate ions in SBF. The amount of ions adsorbing on the vaterite surfaces deposited on PE was larger than that on alumina. This was attributed to differences in the surface charges between PE (? 16 mV) and alumina (+ 38 mV). The phosphate adsorption was predominantly electrostatic therefore related to the surface charge of vaterite particles. The surface charges of substrates may affect the charge of vaterite particles.     

Investigation of sliding wear surfaces in alumina using transmission electron microscopy

In this study, the subsurface microstructure of alumina wear surfaces and the microstructure of agglomerated debris generated from unlubricated sliding wear at room temperature have been investigated through transmission electron microscopy (TEM). Specimens were thinned through the use of a focused ion beam miller (FIB). TEM studies, including analysis of electron diffraction patterns from the agglomerated region of the specimen, revealed the presence of an aggregate of nano crystalline particles embedded in an amorphous phase, together with some larger alumina particles. These larger alumina particles appear at the base of pits in the alumina surface, whereas the finer material appears at the contact surface. The agglomerated debris was readily distinguished from the alumina substrate, which contained localised dislocation damage and microcracking. It is proposed that the wear process involves the removal of ‘large ’ alumina particles from thesurface by a combination of trans- and intergranular microcracking. These particles are then ground into very fine, nanometer-sized particles that react on the surface with moisture in the air to form an amorphous hydroxide film. These are then compacted to form a nanocrystalline structure within an amorphous matrix that may also be viewed as a grain boundary phase.     

Investigation of sliding wear surfaces in alumina using transmission electron microscopy

In this study, the subsurface microstructure of alumina wear surfaces and the microstructure of agglomerated debris generated from unlubricated sliding wear at room temperature have been investigated through transmission electron microscopy (TEM). Specimens were thinned through the use of a focused ion beam miller (FIB). TEM studies, including analysis of electron diffraction patterns from the agglomerated region of the specimen, revealed the presence of an aggregate of nano crystalline particles embedded in an amorphous phase, together with some larger alumina particles. These larger alumina particles appear at the base of pits in the alumina surface, whereas the finer material appears at the contact surface. The agglomerated debris was readily distinguished from the alumina substrate, which contained localised dislocation damage and microcracking. It is proposed that the wear process involves the removal of ‘large’ alumina particles from the surface by a combination of trans- and intergranular microcracking. These particles are then ground into very fine, nanometer-sized particles that react on the surface with moisture in the air to form an amorphous hydroxide film. These are then compacted to form a nanocrystalline structure within an amorphous matrix that may also be viewed as a grain boundary phase.     

Growth of different shape Cu2O micro structures using PEDOT coated ITO electrode

Crystalline cuprous oxide (Cu2O) particles were successfully deposited on poly(3,4-ethylenedioxythiophene) [PEDOT] coated indium tin oxide (ITO) glass. PEDOT film was first prepared on ITO glass by electrochemical polymerization. Crystalline Cu2O particles were then deposited on the PEDOT film by applying various electrochemical synthesis methods using a copper sulfate precursor. The effects of applied electrochemical methods on the compositions, grain sizes and shapes, and surface morphologies of the electrodeposited films were investigated. The micro structures of Cu2O particles were confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). When the cyclic voltammetry (CV) and chronoamperometry (CA) were applied, fine Cu2O particles of cubic and pyramidal phase were formed, respectively. However, bare ITO electrode was used, metallic copper particle was obtained. It shall be assumed that PEDOT might act as a buffer layer in electrochemical reduction of cuprous ion. The details of PEDOT behavior will be the topic of future studies.