Preparation and characterization of reactively sputtered conducting Rh oxide thin films

在Ar和O_2混合气氛中，用反应溅射法制备了Rh氧化物薄膜。采用x射线衍射、x射线光电子能谱和四点探针法研究了溅射参数和沉积后退火对沉积薄膜晶体结构、化学键态和电学性能的影响。在低衬底温度、低溅射功率和低溅射气体压力下，采用纯O_2气体沉积了导电RhO_2薄膜。沉积的RhO_2薄膜结晶性差，电阻率约为300 μΩcm。为了提高薄膜的结晶度和降低电阻率，将沉积的RhO_2薄膜在氧气气氛中退火。结果表明，随着退火温度的升高，RhO_2薄膜的晶粒尺寸增大，电阻率降低。在600 ~ 700℃下退火1 h后，得到了表征金属导电特性的最小电阻率为80 μΩcm和正电阻率温度系数（TCR）。本研究得到的最小电阻率与报道的大块RhO_2的最小电阻率几乎相同。RhO_2薄膜在700℃以下稳定，750℃以上热分解为Rh_2O_3。Rh_2O_3薄膜的电阻率大于1mΩcm， TCR为负，表明Rh_2O_3具有半导体特性。铂族金属的低电阻率导电氧化物如RuO_2和IrO_2，被认为是动态随机存取存储器（DRAM）和铁电RAM （FeRAM）电容器电极的有前途的材料。由于制备了低电阻率（80 μΩcm）的薄膜，因此认为RhO_2适用于电子器件。

Rh oxide thin films were prepared by reactively sputtering a Rh metal target in Ar and O_2 mixed gas atmosphere. Influences of sputtering parameters and post-deposition annealing on crystal structure, chemical bonding state and electrical properties of the deposited thin films were studied by X-ray diffraction, X-ray photoelectron spectroscopy and four-point probe method.Conducting RhO_2 thin films were deposited at low substrate temperatures below 100℃, low sputtering power and low sputtering gas pressure using pure O_2 gas. The as-deposited RhO_2 thin films were poorly crystallized and resistivity of about 300 μΩcm was obtained. In order to improve the crystallinity of the films and reduce resistivity, the as-deposited RhO_2 thin films were annealed in oxygen atmosphere. It was found that the crystal grain size of the RhO_2 thin films increased and the resistivity decreased with increasing annealing temperature. The minimum resistivity of 80 μΩcm and positive temperature coefficient of resistivity (TCR), which indicate metallic conduction characteristics, were obtained for the RhO_2 thin films after annealing at 600-700℃ for 1 hour. The minimum resistivity obtained in this study is almost the same with that reported for bulk RhO_2. The RhO_2 thin films were stable up to 700℃ and thermally decomposed to Rh_2O_3 above 750℃. The resistivity of the Rh_2O_3 thin films was larger than 1mΩcm and negative TCR was observed, which indicate semiconducting characteristics of Rh_2O_3.Low resistivity conducting oxides of platinum group metals, such as RuO_2 and IrO_2, are considered to be promising material for capacitor electrodes of dynamic random access memory (DRAM) and ferroelectric RAM (FeRAM). RhO_2 is thought to be applicable to the electronic devices because thin films of RhO_2 with low resistivity (80 μΩcm) were prepared.