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Production of polarized atomic hydrogen beam and its application to spin-selected Si surface reaction

偏振原子氢束的产生及其在自旋选择硅表面反应中的应用

基本信息

批准号：
09450020
负责人：
NAMIKI Akira
金额：
$ 3.2万
依托单位：
Kyushu Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

Spin polarized atomic hydrogen beam can be obtained with a hexapole magnet. The basic principle is that hydrogen atoms with a magnetic dipole moment receive a force in an inhomogeneous magnetic field. If the atoms have an up-spin state they will receive a force towards the center of the inhomogeneous hexapole magnetic field, while the atoms with a down-spin state will receive a force towards the opposite direction. Thus, the only up-spin state particles can be preferentially focussed after passing a hexapole magnetic field. We produced atomic hydrogen beams from an electron-bombarded W tube. A quadrupole mass spectrometer was used to detect polarized hydrogen atoms. However, we could not get any positive evidence of a focussed polaized beam for the range of magnetic field from a zero to 5000kG. This result should be compared with the case that the supersonic oxygen molecules with a triplet state could be really focussed at the magnetic field of 2-3kGauss. In case of the supersonic oxygen beam the beam is well collimated along the axis of the hexapole maget, while the hydrogen atomic beam from the heated W tube must be defocussed. Therefore, we consider that the failure in focussing the spin polaized hydrogen beam is due to the big divergence of the beam at the entrance of the hexapole magnet. We are now improving the atomic hydrogen source by employing a super sonic expansion of RF plasma.We measured hydrogen atom-induced deuterium abstraction on the Ge(100) surfaces with the unpolarized H beam. This was the preliminary experiment for the spin selected reaction on surfaces. Upon the H beam exposure, HD as well D2 molecules were found to desorb the D/Ge(100) surfaces. We revealed the mechanism of H-induced abstraction and desorption on the semiconductor surfaces.

用六极磁铁可以获得自旋极化的氢原子束。基本原理是具有磁偶极矩的氢原子在非均匀磁场中受到力。如果原子处于上自旋状态，它们将受到一个朝向不均匀六极磁场中心的力，而处于下自旋状态的原子将受到一个朝向相反方向的力。因此，在通过六极磁场之后，唯一的上自旋态粒子可以优先聚焦。我们用电子轰击钨管产生氢原子束。四极质谱仪用于检测极化氢原子。然而，我们无法获得磁场范围从零到5000 kG的聚焦极化束的任何积极证据。这一结果应与具有三重态的超音速氧分子在2- 3 kGauss磁场下能真正聚焦的情况相比较。在超音速氧束的情况下，束沿着六极磁共振的轴被很好地准直，而来自加热的W管的氢原子束必须散焦。因此，我们认为，自旋极化氢束在六极磁铁入口处的大发散是导致聚焦失败的原因。我们利用射频等离子体的超音速膨胀改进了氢原子源，并利用非偏振H束测量了氢原子在Ge（100）表面上的吸氘作用。这是表面自旋选择反应的初步实验。在H束照射下，HD和D2分子在D/Ge（100）表面上脱附。我们揭示了H诱导的提取和解吸的半导体表面上的机制。