Timo Seppänen

Magnetron sputtered epitaxial single-phase Ti3SiC2 thin films

We report on the synthesis and characterization of epitaxial single-crystalline Ti3SiC2 films (Mn+1AXn-phase). Two original deposition techniques are described, (i) magnetron sputtering from Ti3SiC2 compound target and (ii) sputtering from individual titanium and silicon targets with co-evaporated C60 as carbon source. Epitaxial Ti3SiC2 films of single-crystal quality were grown at 900 °C with both techniques. Epitaxial TiC(111) deposited in situ on MgO(111) by Ti sputtering using C60 as carbon source was used to nucleate the Ti3SiC2 films. The epitaxial relationship was found to be Ti3SiC2(0001)//TiC(111)//MgO(111) with the in-plane orientation Ti3SiC2[100]//TiC[101]//MgO[101].

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...

Deviations from Vegard’s rule in Al1−xInxN (0001) alloy thin films grown by magnetron sputter epitaxy

Al1−xInxN (0001) thin films of the pseudobinary AlN–InN system were grown epitaxially onto (111)-oriented MgO wafers with seed layers of Ti1−yZryN by dual direct current magnetron sputtering under ultrahigh vacuum conditions. The relaxed film c-axis lattice parameters determined by x-ray diffraction were studied as a function of composition in the range of 0.07<x<0.82 measured by Rutherford backscattering spectrometry. We find a relative deviation by as much as 37% from the linear dependency described by Vegard’s rule for the lattice parameter versus film composition. The highest relative deviations were found at low InN mole fractions, while the largest absolute deviation was found at x=0.63. This shows that Vegard’s rule is not directly applicable to determine the compositions in the wurtzite Al1−xInxN system.

248 nm cathodoluminescence in Al1- xInxN(0001) thin films grown on lattice-matched Ti1- yZryN(111) seed layers by low temperature magnetron sputter epitaxy

Single-crystal Al0.8 In0.2 N (0001) thin films were grown epitaxially onto lattice-matched Ti0.2 Zr0.8 N (111) seed layers on MgO(111) substrates at 300 °C by magnetron sputter epitaxy. Low-energy ion-assisted epitaxial growth conditions were achieved by applying a substrate potential of -15 V. Cross-sectional high-resolution electron microscopy verified the epitaxy and high-resolution x-ray diffraction ω -rocking scans of the Al0.8 In0.2 N 0002 peak (full width at half maximum ∼2400 arc sec) indicated a high structural quality of the films. Cathodoluminescence measurements performed in a scanning electron microscope at 5 K revealed Al0.8 In0.2 N luminescence at 248 nm, or equivalently 5.0 eV, showing that Al0.8 In0.2 N is a promising material for deep-ultraviolet optoelectronic devices.

Growth of (Zr,Ti)N Thin Films by Ion-Assisted Dual D.C. Reactive Magnetron Sputtering

The ternary nitride (Zr,Ti)N thin films were grown on silicon substrates by ion-assisted dual d.c. reactive magnetron sputtering technique. The substrates were exposed to ion bombardment with varying kinetic energy in the range of 3-103 eV under N/Ar ratio of 1:3. The (Zr0.6Ti0.4)N was formed at all growth conditions. X-ray diffraction measurement indicates the presence of (Zr,Ti)N solid solution with (111) and (200) preferred orientations. The (200) orientation is only present when the films are grown at ion bombardment energies higher than 33 eV. Optimum conditions for film growth produced hardness in the range of 27-29 GPa.

Growth and Characterization of Epitaxial Wurtzite Al1-xInxN Thin Films Deposited by UHV Reactive Dual DC Magnetron Sputtering

Ternary Al1-xInxN thin films were grown by dual target direct current (DC) reactive magnetron sputtering under UHV conditions. The film compositions were determined to range from 0.30

Structural and optical characterization of wurtzite Al0.8In0.2N thin films grown by low temperature magnetron sputter epitaxy

Single-crystal ternary wurtzite Al0.8In0.2N thin films were grown epitaxially onto lattice-matched (111)-oriented Ti0.2Zr0.8N seedlayers. The epilayers were grown onto single-crystal MgO (111) substrates by magnetron sputter epitaxy (MSE) using reactive direct current magnetron sputtering in an N2 discharge under ultra-high-vacuum conditions. The growth temperatures ranged from 20 to 700 oC. Low-energy ion-assisted growth conditions, enhancing the epitaxy, were achieved by applying a negative substrate potential of 15-45 V. Film compositions and lattice parameters were determined using Rutherford Backscattering Spectroscopy (RBS) and High-Resolution X-ray diffraction (XRD), respectively. Cross-sectional High-Resolution Electron Microscopy of the interface regions verified the epitaxy and the crystallinity of the films. XRD ω-rocking scans of the Al0.8In0.2N 0002-peak showed full-width-at-half-maximum values of ~2400 arcs, indicating a high structural quality of the films. Opto-electronical properties were studied by cathodoluminescence at temperatures between 5 and 293 K. Luminescence was observed at wavelengths as short as 248 nm, corresponding to an energy of 5.0 eV. These results point towards the feasibility of metastable Al0.8In0.2N solid solutions as an active luminous material in opto-electronics. It also shows that MSE-grown Al0.8In0.2N can be an excellent choice for lattice-matched GaN heterostructures, with a resulting energy band-gap difference enabling strong charge carrier confinement. In addition to these new and original results, a brief review of the present work on Al(1-x)InxN growth at Linkoeping University is presented.