G. Radnóczi

Electrical and optical properties of CNx(0⩽x⩽0.25) films deposited by reactive magnetron sputtering

The electrical and optical properties of carbon-nitride CNx films (O=x=0.25) deposited by unbalanced reactive magnetron sputtering from a graphite target in mixed Ar/N2 discharges at a substrate te ...

Interfacial reactions in single-crystal-TiN (100)/Al/polycrystalline-TiN multilayer thin films

Abstract The thermal stability of Al/polycrystalline-TiN and Al/single-crystal-TiN couples was investigated using Auger electron spectroscopy (AES) and cross-sectional transmission electron microscopy (XTEM) with energy-dispersive X-ray spectroscopy (EDX). The trilayer samples consisted of a 100 nm thick epitaxial TiN layer grown on MgO(100) substrates, a 100 nm thick aluminium layer, and a 100 nm thick polycrystalline TiN layer. The multilayer films were grown in a dual-magnetron sputter-deposition system and then annealed in a reducing atmosphere at temperatures between 500 and 600 °C for up to 90 min. AES and EDX showed extensive penetration of titanium into the aluminum layer, but only limited interdiffusion of aluminum into both single-crystal and polycrystalline TiN. However, aluminum segregation occurred at both Al/TiN interfaces. XTEM examination revealed the formation of the ordered aluminum-rich AlTi intermetallic compoundssuch as Al 3 Ti in the aluminum layer, while cubic-structure AIN formed at the AlTiN interfaces. Only small differences were observed in the reaction paths and product formation rates of Al/polycrystalline-TiN and Al/single-crystal-TiN couples. AlTi intermetallic compounds formed more rapidly in the former while AIN formation proceeded more rapidly at the Al/single-crystal-TiN interface.

Magnetron sputter epitaxy of wurtzite Al1−xInxN(0.1<x<0.9) by dual reactive dc magnetron sputter deposition

Ternary wurtzite Al1−xInxN thin films with compositions throughout the miscibility gap have been grown onto seed layers of TiN and ZrN by magnetron sputter epitaxy (MSE) using dual reactive direct current magnetron sputter deposition under ultra high vacuum conditions. The film compositions were calculated using Vegard’s law from lattice parameters determined by x-ray diffraction (XRD). XRD showed that single-phase Al1−xInxN alloy films in the wurtzite structure with [0.10<x<0.90] could be obtained at substrate temperatures up to 600°C by heteroepitaxial growth. Epitaxial growth at 600°C gave the crystallographic relations Al1−xInxN(0001)∕∕TiN,ZrN(111) and Al1−xInxN⟨10-10⟩∕∕TiN,ZrN⟨110⟩. At higher substrate temperatures almost pure AlN was formed. The microstructure of the films was also investigated by high-resolution electron microscopy. A columnar growth mode with epitaxial column widths from 10to200nm was observed. Rocking curve full-width-at-half-maximum measurements revealed highly stressed lattices...

Epitaxial growth of Al on Si by thermal evaporation in ultra-high vacuum: growth on Si(100)2 × 1 single and double domain surfaces at room temperature

Abstract Growth of Al on Si(100) in ultra-high vacuum was investigated using in situ RHEED, LEED and AES and ex situ TEM and SEM. The substrates were kept at room temperature during growth. Al was found to grow epitaxially on Si(100)2 × 1 with the orientation relationship Al(110)//Si(100). TEM and RHEED showed that the Al layer had two types of (110)-oriented domains that are 90° rotated with respect to each other in accordance with the following relations Al[001]//Si[011] or Si[011]. RHEED observations during growth demonstrated a continuous change from the original Si(100)2 × 1 pattern to a 1 × 1 pattern after deposition of 2 monolayers (ML). At an Al coverage θ Al = 3 ML , a faint and broad Al-bulk diffraction related intensity was observed in RHEED while a clear Al-bulk diffraction pattern became visible after ~ 4 ML, indicating three-dimensional growth of Al islands. The decay in the Si AES peak-to-peak intensity versus θ A1 could only be modelled by a layer-by-layer growth mode up to θ A 1 = 4 ML . On an off-oriented, essentially single-domain Si(100)2 × 1 surface, an almost single-domain, monocrystalline Al(110) layer was obtained with only a few 90° rotated crystals. Thus the observed Al crystal domains are related to the Si(100)2 × 1 surface domains. The results are explained in terms of Al dimerization on the Si surface and epitaxial growth on the dimerized layer. A growth sequence leading to the growth of Al(110) crystals is also suggested.

Electron diffraction based analysis of phase fractions and texture in nanocrystalline thin films, part III: Application examples

In this series of articles, a method is presented that performs (semi)quantitative phase analysis for nanocrystalline transmission electron microscope samples from selected area electron diffraction (SAED) patterns. Volume fractions and degree of fiber texture are determined for the nanocrystalline components. The effect of the amorphous component is minimized by empirical background interpolation. First, the two-dimensional SAED pattern is converted into a one-dimensional distribution similar to X-ray diffraction. Volume fractions of the nanocrystalline components are determined by fitting the spectral components, calculated for the previously identified phases with a priori known structures. These Markers are calculated not only for kinematic conditions, but the Blackwell correction is also applied to take into account dynamic effects for medium thicknesses. Peak shapes and experimental parameters (camera length, etc.) are refined during the fitting iterations. Parameter space is explored with the help of the Downhill-SIMPLEX. The method is implemented in a computer program that runs under the Windows operating system. Part I presented the principles, while part II elaborated current implementation. The present part III demonstrates the usage and efficiency of the computer program by numerous examples. The suggested experimental protocol should be of benefit in experiments aimed at phase analysis using electron diffraction methods.

Growth and structural characterization of single-crystal (001) oriented MoV superlattices

Abstract Dual target magnetron sputtering has been used to grow single-crysal MoV superlattice structures (SLS) with modulation wavelengths λ ranging from 0.6 to 17.7 nm on (001) oriented MgO substrates held at temperatures Ts between 600 and 900°C. High resolution cross-sectional transmission electron microscopy (HRXTEM) images and comparisions between experimental and calculated X-ray diffraction (XRD) spectra show that SLS with an interface sharpness of ±1 monolayer (±0.15 nm) could be grown for λ ⩽ 4.9 nm and Ts ⩽ 700°C whereas interdiffusion broadened the interfaces for higher Ts values. This interface sharpness was also verified by growing SLS with λ = 0.6 nm (one unit cell of Mo and one of V) which exhibited strong superlattice satellites in both XRD and selected area electron diffraction (SAED), and contrast from the individual layers was also observed in HRXTEM images. For λ > 4.9 nm, HRXTEM images showed non-uniform layers and the XRD peak width (FWHM) increased by 250%.

Growth structure of thin films for perpendicular magnetic recording media

Thin film systems composed of Co-Cr-Nb-Pt, Ti, Co-Zr-Nb, Co-Cr and permalloy layers have been deposited onto glass substrates in order to investigate the correlation between the magnetic behaviour and microstructure. The grains of the Co-Cr-Nb-Pt films show oriented growth on the permalloy grains, whereas their growth is started by the formation of an amorphous layer on a Ti layer. A better magnetic performance was observed when Ti or Zr containing intermadiate layers were applied between the permalloy and Co-Cr-Nb-Pt film.

Epitaxial growth of Al on Si (100) and Si (111) by evaporation in uhv

Abstract Growth of Al on Si(100) and Si(111) in uhv was investigated using in situ RHEED, LEED and AES and ex situ TEM. The substrates were kept at room temperature during growth. Al was found to grow epitaxially on Si(100) 2 × 1 with the orientation relationship Al(110)|Si(100). TEM and RHEED showed that the Al layer has two types of (110) oriented domains that were 90° rotated with respect to each other in accordance with the following relations Al[001]|Si[011] or Si [01 1 ] . The decay in the Si AES peak-to-peak intensity indicated a deviation from a layer-by-layer growth at an Al coverage of ∼4 ML. We suggest that the Al overlayer replicates the double domain Si(100) 2 × 1 surface and thus can map the step structure on the Si surface. On Si(111) Al grew epitaxially following the relation: Al(111)|Si(111), Si [1 1 0]| Al [1 1 0] for most of the film, while a few grains grew according to the relation Al(100)|Si(111) with Al [011]| Si [1 1 0] .

Defects in amorphous and solid phase epitaxial silicon

Abstract The microstructural morphology of amorphous Si (a-Si) layers deposited in ultrahigh vacuum, as well as crystalline Si grown by solid phase epitaxy (SPE), was studied as a function of Al doping and vapour beam incidence angle. The microstructure of the films was investigated using cross-section transmission electron microscopy. All a-Si layers have a columnar structure, with an average column width of ⩽ 5 nm. The direction of the columns abruptly changes with the change of deposition direction and shows local column tilts and void formation at substrate surface irregularities. These built-in defects in the a-Si films also influence the defect structure in epitaxial Si films grown by SPE. Voids are initially aligned along the column directions and extra voids form owing to irregularities of the columnar structure. Doping of amorphous Si with Al to 10 18 −10 20 cm −3 does not leave detectable effects in the amorphous structure itself, but will increase the void density of the re-grown SPE Si layers. Furthermore, segregation of Al resulting in metallic inclusions in the amorphous crystalline interface causes metal induced crystallization of Si at temperatures far below the normal SPE regrowth temperature, thus preventing the formation of single crystalline silicon in a single-step process.

Formation of a-Ge particles with nm dimensions and their behaviour during annealing

Abstract Amorphous Ge particles with nm dimensions were formed by evaporation of germanium in low pressure gas. For the most uniform distribution of particle sizes, the samples were produced in 130 Pa pure nitrogen. The Ge particles produced in this way have a diameter of approximately 10 nm. During the evaporation, the particles assembled in the gas to form long branches. A neck forms at the contact points of the particles and its radius grows in time. The mechanisms which produce this effect have the same driving force: the reduction of the surface area and thus surface free energy of the system. This sintering process becomes more and more pronounced at higher temperatures. This effect was seen in the experiments both on specimens heated in the microscope with focused electron beam and on specimens subjected to a heat treatment in a temperature controlled furnace. The most surprising feature of the process is that Ge remains amorphous after this significant material transport. Crystallization takes place independently from the diffusive processes, and occurs at a temperature about 150°C higher than in thick amorphous Ge layers.