High damage threshold HfO2/SiO2 multilayer mirrors deposited by novel remote plasma sputtering

Sputtering deposition coatings offer significant advantages on electron beam (EB) deposition, including high packing density, environmental stability and extremely low losses. But the inherent high compressive stress affects its application in high power laser system. This paper describes the technical feasibility of high damage threshold laser mirrors deposited by a novel remote plasma sputtering technique. This technique is based on generating intensive plasma remotely from the target and then magnetically steering the plasma to the target to realize the full uniform sputtering. The pseudo-independence between target voltage and target current provides us very flexible parameters tuning, especially for the films stress control. Deposition conditions are optimized to yield fully oxidized and low compressive stress single layer HfO2 and SiO2. The high damage threshold of 43.8 J/cm2 for HfO2/ SiO2 laser mirrors at 1064 nm is obtained. For the first time the remote plasma sputtering is successfully applied in depositing laser mirrors with high performance.     

Tantalum silicide films deposited by dc sputtering

Tantalum disilicide films were deposited by conventional dc sputtering from a nominally stoichiometric cathode. The film characteristics were analyzed by x-ray diffraction, backscatter-ing, electron microprobe and electron transmission microsco-py. The film resistivity and stresses were also measured. The effects of heat treatments up to 1000°C were systematically investigated. After a 1000°C anneal, resistivities of 45-60 μΩcm can be achieved reproducibly. Films deposited on sili-con can be oxidized in a steam atmosphere without inducing significant changes in the silicide layer itself. An attempt is made to explain the oxidation behavior in terms of kinetic factors.     

Low temperature SnO2 films deposited by APCVD

SnO₂ films were deposited by atmospheric pressure chemical vapor deposition (APCVD) on glass substrates using tin tetrachloride as the tin precursor, H₂O vapor and O₃–O₂ as oxidizing agents and O₃–O₂ with HF as the fluorine dopant source. The deposition temperatures varied from 200 to 350 °C. It is shown that the deposition temperature and the oxidizing agent used are related with the structure, optical transmission percent, and resistivities of the films. Finally, films with good transmission percent between 85% and 90% in the visible spectrum and lower resistivities ranged from 0.1 to 0.02 Ω cm are obtained.     

Thickness-dependent optoelectronic properties of CuCr0.93Mg0.07O2 thin films deposited by reactive magnetron sputtering

CuCr_0.93Mg_0.07O₂ thin films were successfully deposited by DC reactive magnetron sputtering at 1123 K from metallic targets. The influence of film thickness on the structural and optoelectronic properties of the films was investigated. X-ray diffraction (XRD) results revealed that all the films had a delafossite structure with no other phases. The optical and electrical properties were investigated by UV–VIS spectrophotometer and Hall measurement, respectively. It was found that the optoelectronic properties exhibited a thickness-dependent behavior. The optical band gap and the average transmittance of the films showed a monotonous decrease with respect to the increase in thickness. The average transmittance in the visible region decreased from 67% to 47% as the thickness increased from ~70 nm to ~280 nm. Simultaneously, the conductivity of the films fell from 1.40 S∙cm⁻¹ to 0.27 S∙cm⁻¹. According to Haacke's figure of merit (FOM), a film with a maximum FOM value of about 1.72×10⁻⁷ Ω⁻¹ can be achieved when the thickness is about 70 nm (σ≈ 1.40 S·cm⁻¹ and T_av. ≈67%).     

Study of amorphous Ta2O5 thin films by DC magnetron reactive sputtering

The dc magnetron reactive sputtering deposition of tantalum pentoxide (Ta₂O₅) thin films was investigated. By combining Schiller's criterion and Reith’s “target preoxidation” procedure, high quality Ta₂O₅ thin films were prepared at a high deposition rate of about lOOÅ;/min. The deposited films were amorphous, with a refractive index around 2.07 and a dielectric constant of 20. An optical transmit-tance of 98.6% was obtained for a 4500Â thick film. The leakage current density is 5 × 10^?9 A/cm² at an electric field strength of 1 MV/cm and its breakdown field strength is above 2 MV/cm. The temperature coefficient of capacitance for capacitors fabricated using the deposited films is approximately +230 ppm/°C. X-ray photoelectron spectroscopy shows that the films are stoichiometric tantalum pentoxide, Ta₂O₅, and exhibit good stability.     

Switching processes and dielectric breakdown in polycrystalline Nb2O5 films

Repetitive resistive switching from the high-to the low-resistance state in thin polycrystalline Nb₂O₅ films was investigated. The switching process, and dielectric breakdown, are associated with four successive conduction states. The thermal activation energy in the first conduction state is 0.35 eV and in the second state is 0.047 eV; in the third and fourth resistance states the temperature coefficient of resistance exhibits metallic behavior. The I-V relationship changes from the Poole-Frenkel mechanism in the first state to space-charge-limited conduction in the second state and a linear relation in the third and fourth states. These and other results indicate that dielectric breakdown occurs through a process of a metallic precipitation increasing in each consecutive state and the formation of a highly conductive filament in the fourth and final state in the dielectric breakdown process. The values of important switching parameters such as the threshold field for switching E_s, holding current and voltage I_h and V_h, switching time τ_s, delay time τ_d and recovery time τ_r are presented. The dependence of the delay time τ_d on the applied voltage and temperature is studied and the relation τ_d∝exp(−k(V/V_s)) is established, with k showing only a slight temperature dependence. Supported by the Office of Naval Research     

负偏压对磁控溅射Mg_2Si薄膜的影响

采用直流磁控溅射加负偏压方法和退火工艺制备了Mg_2Si半导体薄膜,研究了不同负偏压对Mg膜的沉积速率、Mg_2Si薄膜结构以及电阻率的影响。结果表明,随着负偏压的增大,因压实膜层和二次溅射效应,Mg膜的沉积速率越来越小;在未加负偏压时,Mg_2Si薄膜的衍射峰最强、样品表面平整致密,当衬底加上负偏压后,Mg_2Si衍射峰都有所减弱,样品表面变得凹凸不平;当负偏压达到–150 V时,表面已呈现明显的熔融状态,表明负偏压对Mg_2Si薄膜的晶体结构没有有益影响。Mg_2Si薄膜的电阻率随着所加负偏压的增大先减小后增大,并在–90 V时达到最小值。     

贵金属磁控溅射镀膜技术及工艺研究

本文介绍了一种独特的贵重金属溅射靶的结构设计,并在此基础上对贵重金属磁控溅射薄膜工艺进行研究,结果表明新型靶的设计可以有效提高靶材利用率达60%以上,沉积的Au薄膜具有良好的均匀性,且附着力大于25.1 N/mm2.     

Photoelectric properties of ITO thin films deposited by DC magnetron sputtering

As anti-reflecting thin films and transparent electrodes of solar cells,indium tin oxide（ITO） thin films were prepared on glass substrates by DC magnetron sputtering process.The main sputtering conditions were sputtering power,substrate temperature and work pressure.The influence of the above sputtering conditions on the transmittance and conductivity of the deposited ITO films was investigated.The experimental results show that, the transmittance and the resistivity decrease as the sputtering power increases from 30 to 90 W.When the substrate temperature increases from 25 to 150℃,the transmittance increases slightly whereas the resistivity decreases.As the work pressure increases from 0.4 to 2.0 Pa,the transmittance decreases and the resistivity increases.When the sputtering power,substrate temperature and work pressure are 30 W,150℃,0.4 Pa respectively,the ITO thin films exhibit good electrical and optical properties,with resistivity below 10^-4Ω·cm and the transmittance in the visible wave band beyond 80%.Therefore,the ITO thin films are suitable as transparent electrodes of solar cells.     

用直流磁控溅射法制备的ＩＴＯ薄膜的光电性能研究

用直流磁控溅射法将ＩＴＯ薄膜制备在玻璃基片上以作为太阳电池的透明电极。通过改变溅射功率、基片温度和工作气压来研究它们对所沉积的ITO薄膜的透过率和电导率的影响。实验结果表明：当溅射功率从30W增加到90W时,薄膜的透过率和电阻率都将减小;当基片温度从25℃ 增加到 150℃时,透过率稍微有点增大但电阻率减小;当工作气压从0.4Pa 增大到2.0Pa时,透过率减小,但电阻率增大。因此,在溅射功率为30W、基片温度为150℃、工作气压为0.4Pa 时,ITO薄膜有比较好的光电性能,其电阻率小于10-4 Ω•cm ,在可见光波段的透过率大于80%,适合于作为太阳电池的透明电极。     

Thermal conductivity of AlN thin films deposited by RF magnetron sputtering

Aluminum nitride (AlN) film, which is being investigated as a possible passivation layer in inkjet printheads, was deposited on a Si (1 0 0) substrate at 400 °C by radio frequency (RF) magnetron sputtering using an AlN ceramic target. Dependence on various reactive gas compositions (Ar, Ar:H₂, Ar:N₂) during sputtering was investigated to determine thermal conductivity. The crystallinity, grain size, and Al–N bonding changes by the gas compositions were examined and are discussed in relation to thermal conductivity. Using an Ar and 4% H₂, the deposited AlN films were crystalline with larger grains. Using a higher nitrogen concentration of 10%, a near amorphous phase, finer morphology, and an enhanced Al–N bonding ratio were achieved. A high thermal conductivity of 134 W/mk, which is nine times higher than that of the conventional Si₃N₄ passivation film, was obtained with a 10% N₂ reactive gas mixture. A high Al–N bonding ratio in AlN film is considered the most important factor for higher thermal conductivity.     

直流磁控溅射制备非晶硅薄膜的研究

非晶硅薄膜（a-Si）是目前重要的光敏材料,在很多领域得到广泛应用。直流磁控溅射具有工艺简单．沉积温度低等优点,是制备薄膜的一种重要技术。采用直流磁控溅射工艺在玻璃基板上沉积薄膜,并对样品进行了退火处理。研究了沉积速率与溅射功率的关系。结果表明薄膜的沉积速率与溅射功率近似有线性关系。利用X射线衍射（XRD）对薄膜进行了分析鉴定,结果表明溅射的薄膜是非晶硅薄膜。利用扫描电子显微镜（SEM）对非晶硅薄膜的表面形貌进行了观察和分析,与X射线衍射测试的结果一致。所以．利用直流磁控溅射工艺能在常温下能快速制备出良好的非晶硅薄膜。     

衬底温度对磁控溅射生长HMGZO薄膜特性的影响

为适应高效Si基薄膜太阳电池对宽光谱透明导电 薄膜的需求,采用磁控溅射技术 生长了不同衬 底温度氢化作用下Ga和Mg共掺杂ZnO(HMGZO)透明导电氧化物(TCO)薄膜。研究了不同衬底温 度(200～280 ℃)对HMGZO薄膜 结晶特性及光电特性的影响。实验结果表明,制备的HMGZO薄膜均为具有六角纤锌矿结构的 多晶薄膜,呈 现(002)晶面择优生长。随着衬底温度的升高,薄膜中Mg含量逐渐增加,并且薄膜表面新型 锥状结构趋于 致密和均匀化。在各元素含量和结晶质量的共同影响下,其电阻率随着温度的升高从6．70×10－4 Ω·cm增加至7．63×10－4 Ω·cm。所有薄膜在可 见光区域(380～800 nm)的透过率均在80%以上,由于载流子共振吸收的作用,近红外区域的 透过率有所下降。MgO扩展带隙的作用和 Burstein-Moss(BM)效应的影响共同促进了薄膜光学带隙E_g展 宽,使得E_g达到了3.75 eV。当衬底温度为280 ℃ 时,薄膜方块电阻为4.91 Ω/sq,电阻率为7.63×10－4 Ω·cm,光电性能指数ΦTC值达0.022 Ω－1。     

On temperature coefficient of resistance of boron-doped SiGe films deposited by sputtering

Silicon–germanium films, doped with boron, were deposited on oxidised silicon substrates by RF magnetron sputtering. The post-deposition dopant activation and film crystallisation was done by annealing in the temperature range from 580 to 900 °C. The structural changes in the silicon–germanium films caused by the presence of boron and annealing were investigated by high-resolution transmission electron microscopy. The temperature coefficient of resistance (TCR) was characterised in the temperature range from room temperature to 210 °C and correlated to the nano-structure of the films. The TCR values were explained by the contribution of different scattering mechanisms and confirmed by low-frequency noise measurement. Very low values of TCR can be obtained by selecting appropriate boron content and post-deposition annealing conditions.     

Optical properties of amorphous carbon films deposited by magnetron sputtering of graphite

The thermal stability of amorphous carbon (a-C and a-C:H) has been studied by ellipsometry and spectrophotometry in the visible and near-UV range (1.5–5.6 eV). The dielectric function of amorphous carbon has been derived and analyzed using the Kramers-Kronig technique. The conventional analytical approach is shown to be insufficient for the analysis of thermally treated samples. The fundamental absorption edge is analyzed with respect to collective effects in nanoscale fragments of the graphite-like component of the amorphous carbon structure. Two types of graphite-like clusters contributing to the spectral dependence of the fundamental absorption edge and modified by thermal treatment are revealed.     

激光溅射淀积Y-Ba-Cu-O超导薄膜

利用准分子激光束辐照Y-Ba-Cu-O超导靶体,使之元素溅射出来,喷到平行于靶面的基片之上而淀积成膜,然后通过适当的退火过程,所制薄膜在液氮温区具有超导性。制取了零电阻温度85K的高温超导薄膜;讨论了淀积条件与退火过程对薄膜超导性能的影响。     

Low Power MoS2/Nb2O5 Memtransistor Device with Highly Reliable Heterosynaptic Plasticity

Artificial synapses based on 2D MoS₂ memtransistors have recently attracted considerable attention as a promising device architecture for complex neuromorphic systems. However, previous memtransistor devices occasionally cause uncontrollable analog switching and unreliable synaptic plasticity due to random variations in the field-induced defect migration. Herein, a highly reliable 2D MoS₂/Nb₂O₅ heterostructure memtransistor device is demonstrated, in which the Nb₂O₅ interlayer thickness is a critical material parameter to induce and tune analog switching characteristics of the 2D MoS₂. Ultraviolet photoelectron spectroscopy and photoluminescence analyses reveal that the Schottky barrier height at the 2D channel–electrode junction of the MoS₂/Nb₂O₅ heterostructure films is increased, leading to more effective contact barrier modulation and allowing more reliable resistive switching. The 2D/oxide memtransistors attain dual-terminal (drain and gate) stimulated heterosynaptic plasticity and highly precise multi-states. In addition, the memtransistor devices show an extremely low power consumption of ≈6 pJ and reliable potentiation/depression endurance characteristics over 2000 pulses. A high pattern recognition accuracy of ≈94.2% is finally achieved from the synaptic plasticity modulated by the drain pulse configuration using an image pattern recognition simulation. Thus, the novel 2D/oxide memtransistor makes a potential neuromorphic circuitry more flexible and energy-efficient, promoting the development of more advanced neuromorphic systems.     

直流磁控溅射制备非晶硅薄膜的研究

非晶硅薄膜(a-Si)是目前重要的光敏材料,在很多领域得到广泛应用.直流磁控溅射具有工艺简单,沉积温度低等优点,是制备薄膜的一种重要技术.采用直流磁控溅射工艺在玻璃基板上沉积薄膜,并对样品进行了退火处理.研究了沉积速率与溅射功率的关系.结果表明薄膜的沉积速率与溅射功率近似有线性关系.利用X射线衍射(XRD)对薄膜进行了分析鉴定,结果表明溅射的薄膜是非晶硅薄膜.利用扫描电子显微镜(SEM)对非晶硅薄膜的表面形貌进行了观察和分析,与X射线衍射测试的结果一致.所以,利用直流磁控溅射工艺能在常温下能快速制备出良好的非晶硅薄膜.     

共溅射法制备ITO:Zr薄膜及其特性研究

采用ITO靶和Zr靶共溅射在玻璃衬底上沉积了ITO:Zr薄膜,研究了衬底温度、氧流量对ITO:Zr薄膜性能的影响.表征和对比了ITO:Zr薄膜晶体结构和表面粗糙度的变化ITO:Zr薄膜在低温生长时就可以得到良好的光电性能,衬底温度的提高显著改善了薄膜光电性能;一定范围的氧流量也可以改善薄膜的性能,但过量的氧却使得ITO:Zr薄膜的光性能变差.透射谱表明各参数的变化引起了明显的"Burstin Moss"效应.当优化溅射条件为工作气压0.5Pa、氧流量0.3 sccm、直流溅射功率45 W(ITO靶)和射频功率10 W(Z靶)、沉积速率8 nm/min和一定的衬底温度时,可以获得方阻10～20 Ω/sq和可见光透过率85%(含基底)以上的ITO:Zr薄膜.