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NMR Studies of Amorphous Silicon and Aluminosilicate Glass William Wel-Lin Shao Iowa State University

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NMR Studies of Amorphous Silicon and Aluminosilicate Glass William Wel-Lin Shao Iowa State University Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1989 NMR studies of amorphous silicon and aluminosilicate glass William Wel-Lin Shao Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Physical Chemistry Commons Recommended Citation Shao, William Wel-Lin, "NMR studies of amorphous silicon and aluminosilicate glass " (1989). Retrospective Theses and Dissertations. 9178. https://lib.dr.iastate.edu/rtd/9178 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. INFORMATION TO USERS The most advanced technology has been used to photo­ graph and reproduce this manuscript from the microfilm master, UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. 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Ml 48106-1346 USA 313/761-4700 800/521-0600 Order Number 0014963 NMR studies of amorphous silicon and aluminosilicate glass Shao, William Wei-Lin, Ph.D. Iowa State University, 1989 UMI 300N.ZeebRA Ann Arbor, MI 48106 HMR studies of amorphous silicon and aluminosilicate glass by William Wei-Lin Shao A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Department: Chemistry Major: Physical Chemistry Approved: Signature was redacted for privacy. In Charge of Major Work Signature was redacted for privacy. 3r the Major Department Signature was redacted for privacy. Fo^/^he Graduate College Iowa State University Ames, Iowa 1989 ii TABLE OF CONTENTS Page INTRODUCTION 1 PART ONE. NMR STUDIES OF ZERODUR 3 INTRODUCTION 4 LITERATURE REVIEW 6 Structure of Silicate and Aluininosilicate Glasses 6 29si NMR Studies of Silicates and Aluminosilicates 11 NMR Studies of Aluminosilicates 20 Theoretical Background and Consideration 25 EXPERIMENTAL 33 Consideration 33 Probe Construction 35 Experimental 41 RESULTS AND DISCUSSION 43 CONCLUSIONS 56 REFERENCES 77 PART TWO. NMR STUDIES OF AMORPHOUS SILICON 83 INTRODUCTION 84 LITERATURE REVIEW 85 EXPERIMENTAL 93 RESULTS AND DISCUSSION 95 iii CONCLUSIONS 104 REFERENCES 117 CONCLUSIONS 119 ACKNOWLEGEMENTS 121 LIST OF FIGURES PART ONE. NMR STUDIES OF ZERODUR Page Figure 1. Theoretical quadrupole powder patterns 57 Figure 2. Spin system assembly 58 Figure 3. Stator and air bearing ring 59 Figure 4. Rotor 60 Figure 5. Stator seat and stator 61 Figure 6. The circuit for spinning speed measurement 62 Figure 7. Magic angle adjustment. 63 Figure 8. Rotational echos of "^^Br in KBr at magic angle 64 Figure 9. The probe circuit 65 Figure 10. MAS NMR spectrum of ZERODUR taken with 90 degree pulse and 700 seconds recycle time 66 Figure 11. MAS NMR spectrum of ZERODUR taken with 90 degree pulse and 200 seconds recycle time 67 Figure 12. MAS NMR spectrum of ZERODUR taken with 4 degree pulse and 50 seconds recycle time 68 Figure 13. MAS NMR spectrum of ZERODUR taken with 4 degree pulse and 50 seconds recycle time 69 Figure 14. Z^Al MAS spectrum of ZERODUR taken at 57 MHz 70 Figure 15. Z^Al MAS spectrum of glass 2 taken at 57 MHz 71 Figure 16. ^^Al MAS spectrum of ZERODUR taken at 77 MHz 72 Figure 17. ^^Al MAS spectrum of glass 2 taken at 77 MHz 73 Figure 18. Z^Al MAS spectrum of ZERODUR taken at 130 MHz 74 V PART TWO. NMR STUDIES OF AMORPHOUS SILICON Figure 1. X-ray diffraction pattern of a-Si without annealing 105 Figure 2. X-ray diffraction pattern of a-Si after annealing at 580 °C 106 Figure 3. X-ray diffraction pattern of a-Si after annealing at 610 °C 107 Figure 4. X-ray diffraction pattern of a-Si after annealing at 640 °C 108 Figure 5. X-ray diffraction pattern of a-Si after annealing at 640 °C 109 Figure 6. Relative spin density of a-Si vs annealing temperature 110 Figure 7. MAS NMR spectrum of a-Si after annealing at 580 'C 111 Figure 8. MAS NMR spectrum of a-Si after annealing at 610 "C 112 Figure 9. MAS NMR spectrum of a-Si after annealing at 640 "C 113 Figure 10. The longitudinal relaxation time of a-Si vs annealing temperature 114 Figure 11. The first moment of NMR spectrum of a-Si vs annealing temperature 115 Figure 12. The relative second moment of NMR spectrum of a-Si vs annealing temperature 116 vi LIST OF TABLES Table 1, Fit parameters for the ^Sgi NMR spectrum of ZERODUR taken with a recycle time of 700 seconds 75 Table 2. Fit parameters for the Zggi NMR spectrum of ZERODUR taken with a recycle time of 200 seconds 75 Table 3, Fit parameters for the ^^Si NMR spectrum of ZERODUR taken with a recycle time of 50 seconds and a flip angle of 4 degree 76 Table 4, Fit parameters for the NMR spectrum of Glass 2 taken with a recycle time of 50 seconds and a flip angle of 4 degree 76 1 INTRODUCTION There exists a wide range of different amorphous solids each with its own unique structure. Since amorphism is a metastable state of matter, their structures depend not only on composition but also on thermal history. The only aspect these materials have in common is their complete lack of long range order. The field of amorphous solids is an area not amenable to most of the conventional theoretical techniques of solid-state physics. For many years amorphous solids were difficult systems to describe as there is no ideal structure which can be accepted with complete confidence and can be used as a starting point for a determination of the concentration of various types of defects and impurities as deviations from the ideal structure as in the situation of a crystal. The word "amorphous" means "structureless", hence to seek a reproducible measurement on such a material is perhaps not totally meaningful. In the past two decades Nuclear Magnetic Resonance (NMR) spectroscopy has became one of the most -powerful techniques for investigating the magnetic and electronic interactions present in a wide variety of materials. In particular, the technique of magic angle spinning (MAS) NMR has been used to obtain high-resolution spectra of solids. The broadening effect of the dipole-dipole interaction and the anisotropic part of the chemical shielding tensor is removed by rapid 2 rotation of sample at the "magic angle" (54.7°) with respect to the magnetic field. Also the broadening due to electric field gradients on quadrupolar nuclei is reduced. In this thesis, the capabilities of NMR were utilized to probe the local structure and local ordering in an aluminosilicate glass sample and an amorphous Si sample. 3 PART ONE. NMR STUDIES OF ZERODUR 4 INTRODUCTION Aluminosilicate glasses have been industrially produced and widely used in daily life for hundreds of years. The chemical and physical properties of aluminosilicates are of commercial and theoretical interest. A detailed knowledge of the structure of these materials is needed to better understand their properties and to improve them to produce new glasses. A glass is presumed to be the quenched equivalent of a melt. That is, the structure of the melts at the glass transition temperature is retained in the glass state, except that the molecular motions characterizing the liquid state are no longer present. Thermodynamically, a melt is substantially different from the glass because of the dynamics present in the molten state. NMR spectroscopy which is very sensitive to the local electron environments surrounding nonzero spin nuclei(1) has proven invaluable in determination of silicon-aluminum local ordering in aluminosilicate glasses . X-ray diffraction techniques have difficulty, even in single crystals, distinguishing aluminum atoms from silicon atoms because their atomic radii are almost identical and they can occupy the same structural positions. The only differentiating feature is that the Al-0 bond length is slightly longer than that of Si-0. This difference is not possible to distinguish in many aluminosilicate structures. Both 29si and ^"^Al NMR have been of great value in 5 investigations of aqueous, crystalline, glassy and molten aluminosilicate structures. In particular, the technique of magic angle spinning (MAS) NMR has been used to obtain high-resolution spectra of solids.
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