Structural characterization of a-plane Zn1−xCdxO (⩽x⩽0.085) thin films grown by metal-organic vapor phase epitaxy

Abstract

Zn 1−x Cd x O͑1120͒ films have been grown on ͑0112͒ sapphire ͑r-plane͒ substrates by metal-organic vapor phase epitaxy. A 800-nm-thick ZnO buffer, deposited prior to the alloy growth, helps to prevent the formation of pure CdO. A maximum uniform Cd incorporation of 8.5 at. % has been determined by Rutherford backscattering spectrometry. Higher Cd contents lead to the coexistence of Zn 1−x Cd x O alloys of different compositions within the same film. The near band-edge photoluminescence emission shifts gradually to lower energies as Cd is incorporated and reaches 2.93 eV for the highest Cd concentration ͑8.5 at. %͒. The lattice deformation, due to Cd incorporation, has been described using a new reference frame in which the lattice distortions are directly related to the a-plane surface structure. Cd introduction does not affect the c lattice parameter but expands the lattice along the two perpendicular directions, ͓1120͔ and ͓1100͔, resulting in a quadratic volume increase.

On the interplay of point defects and Cd in non-polar ZnCdO films

“…In metal-organic vapor phase epitaxy (MOVPE), non-polar ZnCdO films up to 8.5% of Cd can be introduced before domains with different Cd contents are observed in high resolution X-ray diffraction (HRXRD) measurements. 8 Nevertheless, in MOVPE ZnCdO thin films grown over c-sapphire with a ZnO/GaN template, the formation of nanodomains of wurtzite ZnCdO with different Cd fractions has been reported. 9 In non-polar ZnCdO films, the problems due to the polar character of Zn(Cd)O, 10,11 like spontaneously generated electric fields or the increased concentration of defects near the interface with the substrate, are avoided.…”

“…9 In non-polar ZnCdO films, the problems due to the polar character of Zn(Cd)O, 10,11 like spontaneously generated electric fields or the increased concentration of defects near the interface with the substrate, are avoided. 8,12 In this work, the effect of introducing Cd in non-polar MOVPE ZnO films grown over m-and r-plane sapphire with Cd atomic fractions ranging up to 5% is studied by means of slow positron annihilation spectroscopy (SPAS) and a combination of Rutherford backscattering spectroscopy (RBS) and secondary ion mass spectroscopy (SIMS). SPAS is specially well suited for the study of acceptor type vacancies in thin films and SIMS in combination of RBS is capable to measure the Cd depth profile in detail, specifically in the vicinity of the ZnCdO/ZnO buffer interface.…”

ZnO Nanorods Grown on CdxZn1-xO Seed Layers with Various Cd Mole Fractions

“…The Cd (104) diffraction peak is attributed to a little non-oxidized Cd. 8 The Cd (104) diffraction peak was observed from the Cd x Zn 1-x O seed layers (0.25 ≤ x ≤ 0.75), which might be due to the difference in structure of the ZnO and CdO. The radius of the Zn 2+ (0.60 Å) and Cd…”

Structural, morphology and optical properties of Zn(1-x)CdxO solid solution grown on c-plane sapphire substrate

“…The layer is grown in horizontal MO-CVD reactor at atmospheric pressure under N Cadmium (DMCd) and tertiary butanol (terof 380° C. The growth conditions are described elsewhere [13]. With similar growth directly deposited on c-plane sapphire substrates from Crystec.…”