Comparison of interfacial and electronic properties of annealed Pd/SiC and Pd/SiO2/SiC Schottky diode sensors
Comparison of interfacial and electronic properties of annealed Pd/SiC and Pd/SiO2/SiC Schottky diode sensors
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DOI：
10.1116/1.580600
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发表时间：
1997-05-01
影响因子：
2.9
通讯作者：
Knight, D
中科院分区：
文献类型：
--
作者：
Chen, LY;Hunter, GW;Knight, D
由沉积在碳化硅上的钯组成的肖特基二极管(Pd/SiC)在高温下以高灵敏度检测氢气和碳氢化合物气体。先前对Pd/SiC结构的性能的检测表明，即使在425℃下延长热处理后，其正向电流对氢的存在也有响应。然而，传感器性能的漂移表明，二极管结构的稳定是必要的。在这项工作中，我们研究了在Pd和SIC之间放置一层薄薄的二氧化硅(SiO_2)的效果。对Pd/SiC和Pd/SiO_2/SiC二极管在425℃下进行140h的退火处理，比较了退火后二极管的电学性质和界面性质。两种二极管的电子性质和氢气灵敏度都因退火而发生了显著的变化。扫描电子显微镜和俄歇电子能谱表明，二极管的表面和界面性质有很大的不同。Pd/SiC二极管与分布在整个Pd中的Pd硅化物(PdxSi)具有较宽的界面区域。相比之下，Pd/SiO_2/SiC二极管具有尖锐的界面，形成的PdxSi明显较少。在Pd的近表面区域形成了一层硅氧化物(SiOx)层，这可能是Pd/SiO_2/SiC二极管对氢相对不敏感的原因。实验数据表明，这种SiOx的形成机制可能是Pd和周围的碳化硅表面之间的二维扩散。虽然薄薄的SiO_2层在Pd和SiC之间形成了尖锐的界面，但二极管结构的进一步稳定对于高温传感器的长期运行是必要的。(C)1997年美国真空协会。
Schottky diodes composed of palladium deposited on silicon carbide (Pd/SiC) detect hydrogen and hydrocarbon gases at elevated temperatures with high sensitivity. Previous examination of the properties of the Pd/SiC structure indicated that its forward current responded to the presence of hydrogen even after extended annealing at 425 degrees C. However, drift in the sensor properties suggested that stabilization of the diode structure was necessary. In this work, we examine the effects of placing a thin layer of silicon dioxide (SiO2) between the Pd and the SiC. Both Pd/SiC and Pd/SiO2/SiC diodes are annealed at 425 degrees C for 140 h and the electronic and interfacial properties of the annealed diodes are compared. The electronic properties and sensitivity to hydrogen of both diodes change significantly due to the annealing. Scanning electron microscopy and Auger electron spectroscopy indicate that the surface and interfacial properties of the diodes are very different. The Pd/SiC diode has a broad interface region with palladium silicides (PdxSi) distributed throughout the Pd. In contrast, the Pd/SiO2/SiC diode has a sharp interface with significantly less PdxSi formation. A silicon oxide (SiOx) layer has formed in the near surface region of the Pd which likely accounts for the relative insensitivity of the Pd/SiO2/SiC diode to hydrogen. The experimental data suggest that the mechanism for this SiOx formation is likely two-dimensional diffusion between the Pd and the surrounding SiC surface. While the thin SiO2 layer results in a sharp interface between the Pd and SiC, further stabilization of the diode structure is necessary for long term, high temperature sensor operation. (C) 1997 American Vacuum Society.