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Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Nano-regime Length Scales Extracted from the First Sharp Diffraction Peak in Non-crystalline SiO2 and | Nanoscale Res Lett 2010 5 550-558 DOI 10.1007 s11671-009-9520-6 SPECIAL ISSUE ARTICLE Nano-regime Length Scales Extracted from the First Sharp Diffraction Peak in Non-crystalline SiO2 and Related Materials Device Applications Gerald Lucovsky James C. Phillips Received 11 September 2009 Accepted 17 December 2009 Published online 6 January 2010 The Author s 2010. This article is published with open access at Springerlink.com Abstract This paper distinguishes between two different scales of medium range order MRO in non-crystalline SiO2 1 the first is 0.4 to 0.5 nm and is obtained from the position of the first sharp diffraction peak FSDP in the X-ray diffraction structure factor S Q and 2 the second is 1 nm and is calculated from the FSDP full-width-at-half-maximum FWHM. Many-electron calculations yield Si-O third- and O-O fourth-nearest-neighbor bonding distances in the same 0.4-0.5 nm MRO regime. These derive from the availability of empty Si dp orbitals for back-donation from occupied O pp orbitals yielding narrow symmetry determined distributions of third neighbor Si-O and fourth neighbor O-O distances. These are segments of six member rings contributing to connected six-member rings with 1 nm length scale within the MRO regime. The unique properties of non-crystalline SiO2 are explained by the encapsulation of six-member ring clusters by five-and seven-member rings on average in a compliant hard-soft nano-scaled inhomogeneous network. This network structure minimizes macroscopic strain reducing intrinsic bonding defects as well as defect precursors. This inhomogeneous CRN is enabling for applications including thermally grown 1.5 nm SiO2 layers for Si field effect transistor devices to optical components with centimeter dimensions. There are qualitatively similar length scales in nano-crystalline HfO2 and phase separated Hf silicates based on the primitive unit cell rather than a ring structure. G. Lucovsky El Department of Physics North Carolina State .
