High-pressure study of silane to 150 GPa
- CIW
We present an extensive study of the optical, electronic, and structural properties of silane (SiH{sub 4}) to 150 GPa through the use of Raman spectroscopy, optical microscopy, synchrotron infrared reflectivity, optical absorption, and synchrotron x-ray diffraction measurements. To mitigate possible contamination from previously reported metal hydride formation, we performed experiments using gold-lined sample gaskets, finding molecular silane remains in the transparent and insulating P2{sub 1}/c structure until {approx}40 GPa. Silane shows a partial loss of crystallinity above {approx}50 GPa and appears to visibly darken. The darkening is plausibly the result of a loss of molecular character with many enthalpically competitive pathways available, including decomposition, combined with the absorptive nature of the sample. Above 100 GPa we observed crystallization into structures partially consistent with the previously reported nonmolecular I4{sup -} 2d and I4{sub 1}/a types. In the absence of decomposition, silane remains partially transparent and nonmetallic to at least 150 GPa with a band gap constrained between 0.6 and 1.8 eV. Under pressure, silane is sensitive to irradiation from x-rays and lasers, and may easily decompose into metallic silicon. We suggest that previous reports of metallization starting from molecular SiH{sub 4} arise from decomposition, and superconductivity may originate from hydrogen-doped silicon. While silane may readily decompose, the inherent metastability provides access to a wide range of path- and sample-history-dependent states and suggests a unique range of physical properties for hydrogen-rich silicon alloys.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- NSFOTHERDOE - BASIC ENERGY SCIENCESU.S. ARMY RESEARCHNASA
- OSTI ID:
- 1022270
- Journal Information:
- Phys. Rev. B, Vol. 83, Issue (14) ; 04, 2011; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- ENGLISH
Similar Records
Surface chemistry of epitaxial-silicon deposition by thermal cracking of silane
Hydrogen-dominated plasma, due to silane depletion, for microcrystalline silicon deposition