R.J. Gaboriaud

Yttrium oxide thin films, Y2O3, grown by ion beam sputtering on Si

Thin films of yttrium sesquioxide, Y2O3, have been deposited on Si by ion beam sputtering at room temperature and 700 °C under an oxygen pressure of 4×10-3 Pa or by oxygen ion beam assisted deposition. The stoichiometry of these films was analysed by Rutherford backscattering spectrometry. The thickness and refractive index of the oxide were studied as functions of the wavelength by ellipsometry. The crystalline orientations of the deposited films were determined by x-ray diffraction. The micro- and nano-structure were investigated by transmission electron microscopy on cross section samples.

Yttrium sesquioxide, Y2O3, thin films deposited on Si by ion beam sputtering: microstructure and dielectric properties

Abstract Y2O3 thin films were in-situ deposited by ion beam sputtering on Si substrate. The influence of the deposition parameters are studied by X-ray diffraction, electrical measurements and high resolution transmission electron microscopy observations. The stress sate of the oxide layers is investigated by the sin2ψ method as a function of the deposition parameters and the post-annealing treatments. Oxygen ion beam assisted deposition process or post-annealing of as-deposited thin films lead to the same relaxation of the internal compressive stress within the oxide layer. An SiO2 layer sandwiched between Si and Y2O3 is always observed and should play a role both in the growing process and electrical properties of the MOS structure based on Y2O3 oxide layer. The results are interpreted in terms of diffusional process in the oxide, which are directly related to the temperature and the oxygen partial pressure during the growth process.

Interfacial reactions in Y2O3 thin films deposited on Si(100)

Abstract Interfacial reactions in thin films of Y 2 O 3 on Si(100) have been studied by means of energy dispersive X-ray analysis and high resolution transmission electron microscopy observations. Thin films of yttrium oxide were deposited at 700 °C by ion beam sputtering and then annealed at 700 and 900 °C under vacuum and in air, respectively. After an annealing treatment of 2 h at 900 °C in air a solid-state amorphization is observed at the interface Y 2 O 3 /SiO x . After annealing at 700 °C under vacuum a surprising phenomenon of electron beam irradiation induced epitaxial reconstruction is observed at the Si substrate surface.

Dislocation core and pipe diffusion in Y2O3

Little is known about the dislocation core and the related pipe diffusion in oxides. Interesting features can be gained from irradiation induced defect nucleation along dislocation lines. In yttrium sesquioxide Y2O3, it is observed that the pipe diffusion is the driving force of nucleation of extended defects which involves the diffusion of both ions, metal and oxygen. A periodic distribution of defects along the dislocation is interpreted in terms of dislocation core instability based on the effect known as Rayleigh instability.

Microstructure imaging of the YBCO thin film/MgO substrate interface : HRTEM and Fourier analysis of the Moiré fringe pattern

Detailed microstructural aspects of the interface between YBaCuO thin films and MgO substrate are studied by means of a Fourier analysis of Moire fringe pattern obtained from HRTEM investigations of plan view samples. The main features of the observations are large, well oriented crystallographic domains surrounded by wide boundaries. HRTEM investigations together with the Fourier analysis show evidence of both orthorhombic and pseudo-tetragonal structure in the YBaCuO film. An accommodation mechanism is suggested from the Fourier analysis of the Moire fringe pattern.

Optical and digital processing of H.R.T.E.M. images of Si thin films deposited by R.T.C.V.D.

Thin films of Si deposited by R.T.C.V.D. on (001) Si wafer were investigated on cross sectional sample using a JEOL 3010 high resolution microscope, in order to study the epitaxy and extended lattice defects formed during the deposition process in the film. H.R.T.E.M. images of extended defects were investigated by optical Fourier analysis in different areas of the picture; the results are interpreted in terms of twins and periodicity of twin lamellae. Further analysis from digital processing of the H.R.T.E.M. pictures was done by Gabor filtering and is interpreted in terms of strain field in the matrix.

Composition of thin films deposited by ion beam sputtering of a compound target: case of YBaCuO

Abstract The composition of thin films deposited by ion beam sputtering, using a Kaufman source, of a compound target is studied through the example of YBaCuO. The following factors governing the sputtering process are investigated: temperature of the target; the flux of sputtered particles which condense on the substrates; the experimental angular distribution of the sputtered atomic species coming from the target; the resputtering of the growing films by backscattered primary rare-gas atoms. The angular distribution of ejected atoms is shown to be strongly peaked in the specular direction with respect to the incident high energy beam. This anisotropic distribution turns out to be the main factor governing the final stoichiometry expected in the deposited thin films.

Stress relaxation in c⊥–c// YBaCuO thin films on MgO substrate studied by LACBED

Abstract Thin films of YBaCuO grown by in situ pulsed laser deposition on MgO substrate are studied by means of high resolution transmission electron microscopy imaging and large angle convergent beam electron diffraction experiments. Both c // and c ⊥ YBaCuO crystals coexist in the film. The diffraction experiments are performed on the MgO substrate along the interface with the YBaCuO film. Some of the Bragg lines exhibit a dramatic broadening when the electron probe is just below the c // oriented crystal. This result is interpreted in terms of lattice strain relaxation due to the thinning of the TEM sample. This relaxation phenomenon indicates that the c // oriented grains embedded in a c ⊥ oriented host matrix of YBaCuO, are under stress.

Angular distribution of ion-beam-sputtered elements from an YBa2Cu3O7−x target

The difference in composition of thin films sputter deposited at room temperature caused by the angular distribution of the sputtered elements is studied in the case of an YBa2Cu3O7−x target. The distribution is experimentally determined by means of a semi-cylindrical holder allowing the investigation of angles in the range −10° to 70°. Analysis of the samples, realized mainly by Rutherford backscattering spectrometry, shows that the sputtered elements exhibit a strongly peaked distribution near the specular direction with respect to the incident beam. Stoichiometries of the thin deposited films are deduced and discussed as a function of the angle of ejected matter.

Laser deposition of YBaCuO thin films: stress measurements and microstructure investigations

Abstract Superconducting thin films of YBaCuO have been deposited by laser ablation at 750°C on MgO (001) single crystals. X-ray pole figures indicate a high crystalline quality of c-axis oriented films. A four-circle X-ray goniometer has been used for the measurements of the internal stress in the films by means of the fundamental metric tensor method generally used in the field of continuum mechanics. Microstructural investigation has been done by HRTEM on plan-view samples in order to study the film–substrate epitaxy relations from the observation of the moire pattern brought about by the superimposition of both YBaCuO and MgO lattices (9% misfit). The results are discussed in terms of crystallographic accommodation and stress relaxation between the film and the substrate.