Hashimoto H, Nakajima K, Suzuki M, Sasakawa K, Kimura K
Department of Micro Engineering, Kyoto University, Kyoto 606-8501, Japan.
Rev Sci Instrum. 2011 Jun;82(6):063301. doi: 10.1063/1.3594095.
The sensitivity (limit of detection) of high-resolution Rutherford backscattering spectroscopy (HRBS) is mainly determined by the background noise of the spectrometer. There are two major origins of the background noise in HRBS, one is the stray ions scattered from the inner wall of the vacuum chamber of the spectrometer and the other is the dark noise of the microchannel plate (MCP) detector which is commonly used as a focal plane detector of the spectrometer in HRBS. In order to reject the stray ions, several barriers are installed inside the spectrometer and a thin Mylar foil is mounted in front of the detector. The dark noise of the MCP detector is rejected by the coincidence measurement with the secondary electrons emitted from the Mylar foil upon the ion passage. After these improvements, the background noise is reduced by a factor of 200 at a maximum. The detection limit can be improved down to 10 ppm for As in Si at a measurement time of 1 h under ideal conditions.
高分辨率卢瑟福背散射光谱（HRBS）的灵敏度（检测限）主要由光谱仪的背景噪声决定。HRBS中背景噪声有两个主要来源，一个是从光谱仪真空腔内壁散射的杂散离子，另一个是微通道板（MCP）探测器的暗噪声，在HRBS中该探测器通常用作光谱仪的焦平面探测器。为了阻挡杂散离子，在光谱仪内部安装了几个屏障，并在探测器前面安装了一层薄聚酯薄膜。通过与离子通过时从聚酯薄膜发射的二次电子进行符合测量，来消除MCP探测器的暗噪声。经过这些改进，背景噪声最多可降低200倍。在理想条件下，测量时间为1小时时，硅中砷的检测限可提高到10 ppm。
