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X-ray rocking curve and ferromagnetic resonance investigations of ion-implanted crystals

Citation

Speriosu, Virgil S. (1983) X-ray rocking curve and ferromagnetic resonance investigations of ion-implanted crystals. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-10072002-110622

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. A kinematical model for general Bragg case x-ray diffraction in nonuniform films is presented. The model incorporates depth-dependent strain and structure factor. For ion-implanted crystals the change in structure factor attributed to damage is calculated using a spherically symmetric Gaussian distribution of incoherent atomic displacements. Profiles of strain and structure factor are obtained by fitting experimental rocking curves. The method is applicable to ion-implanted, diffused and multilayer crystalline structures such as heterojunctions and superlattices. A comparison is made between profiles of strain and incoherent atomic displacements obtained from rocking curves and from Rutherford backscattering spectrometry in a Gd3Ga5O12 crystal implanted with 100 keV Ne+. The ranges of sensitivity of the two techniques-overlap for about one decade in implantation dose up to the amorphous threshold. Xray diffraction was found to be most sensitive to low damage levels while backscattering was found to be most sensitive to high damage levels. The two techniques are in excellent agreement on the near-surface strain, but differ significantly at depths below [...]. The discrepancy is attributed to errors caused by steering of channelled particles in backscattering spectrometry. The profiles of number of displaced atoms agree within a factor of two. The rocking curve method is combined with analysis of ferromagnetic resonance (FMR) spectra for characterization of crystalline and magnetic properties of [111]-oriented Gd,Tm,Ga:YIG films implanted with Ne+, He+, and H2+. For each implanted species the range of doses begins with easily-analyzed effects and ends with paramagnetism or amorphousness. Profiles of normal strain, lateral strain and damage were obtained. For maximum strains up to 1.3% the behavior of the strain with annealing is nearly independent of implanted species or dose. Magnetic profiles obtained before and after annealing were compared with the strain profiles. The local change in uniaxial anisotropy field [delta H subscript k] with increasing strain shows an initially linear rise for both He+ and Ne+, in quantitative agreement with the magnetostriction effect estimated from the composition. For strain values between 1% and 1.5%, [delta H subscript k] saturates and for increasing strain, [delta H subscript k] decreases to nearly zero when the material becomes paramagnetic. For peak strains greater than 1.3% for He + and 1.1% for Ne+ the relation between uniaxial anisotropy and strain is not unique. Behavior of the saturation magnetization [4piM], the exchange constant A and the cubic anisotropy [H subscript 1] was elucidated. For [delta H subscript k] implantation the total [delta H subscript k] consists of a magnetostrictive contribution due to strain and of a comparable excess contribution associated with the local concentration of hydrogen. The profile of excess [delta H subscript k] agrees with calculated LSS range. The presence of hydrogen results in a reduction of [4piM] not attributable to strain or damage. With increasing annealing temperature the excess [delta H subscript k] diminishes and above 400?C the only component of [delta H subscript k] is magnetostrictive. Crystalline properties of Si-implanted [100] GaAs, Si, and Ge were studied by the rocking curve method. Sharp qualitative and quantitative differences were found between the damage in GaAs on one hand and Si and Ge on the other. At a moderate damage level the GaAs crystal undergoes a transition from elastic to plastic behavior. The plastically deformed region presents a barrier to epitaxial regrowth and is consistent with the well-known high defect density in regrown GaAs.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:x-ray diffraction; rocking curve; double-crystal; curve fitting; thin films; garnet; magnetic; kinematical diffraction theory; ion implantion; gadolinium gallium garnet; magnetic garnet; single crystal; strain; damage; yttrium iron garnet; annealing; liquid phase epitaxy; GaAs; Si; Ge; Ne+; He+; H+; ferromagnetic resonance; FMR; X-band; magnetostriction; uniaxial anisotropy; magnetization exchange constant; gyromagnetic ratio; paramagnetic; cubic anisotropy; plastic deformation
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Applied Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Wilts, Charles H.
Thesis Committee:
  • Unknown, Unknown
Defense Date:1 January 1983
Record Number:CaltechETD:etd-10072002-110622
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-10072002-110622
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3948
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:07 Oct 2002
Last Modified:26 Dec 2012 03:04

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