Semiconductor Physics, Quantum Electronics & Optoelectronics. 2014. V. 17, N 3. P. 275-283.
https://doi.org/10.15407/spqeo17.03.275

                                                                 

Optical and structural studies of phase transformations and composition fluctuations at annealing of Zn1-xCdxO films grown by dc magnetron sputtering
O. Kolomys1,*, A. Romanyuk1 , V. Strelchuk1 , G. Lashkarev2 , O. Khyzhun2, I. Timofeeva 2, V. Lazorenko2, V. Khomyak3

1V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine,
41, prospect Nauky, 03028 Kyiv, Ukraine
* Corresponding author phone/fax: +38 (044)-525-6473; e-mail: olkolomys@gmail.com
2I. Frantsevich Institute for Problems of Materials Science, NAS of Ukraine,
3, Krzhizhanovsky str., 03680 Kyiv, Ukraine
3 Chernivtsi National University, 2, Kotsiubinsky str., 58012 Chernivtsi, Ukraine

Abstract. Ternary Zn1-xCdx O (x ⟨ 0.12) alloy crystalline films with highly preferred orientation (002) have been successfully deposited on sapphire c-Al2O3 substrates using the direct current (dc) reactive magnetron sputtering technique and annealed at temperature 600 °C in air. The structural and optical properties of Zn1-xCdxO thin films were systematically studied using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), micro-Raman and photoluminescent (PL) spectroscopy. XPS measurements clearly confirmed Cd incorporation into ZnO lattice. XRD data revealed that the growth of wurtzite Zn1-xCdxO films occurs preferentially in the (002) direction. Also, when the Cd content is increased, the XRD peaks shift towards smaller angles and the full width at half-maximum of the lines increases. When the Cd content increases, A 1 LO ( Zn1-xCdxO )-like Raman modes show composition dependent frequency decrease and asymmetrical broadening. The near band-edge PL emission at room temperature shifts gradually to lower energies as the Cd content increases and reaches 2.68 eV for the highest Cd content (x = 0.12). The analysis of NBE band emission and Raman A 1 LO ( Zn1-xCdxO) mode shows that at a higher Cd content the coexistence of Zn1-xCdxO areas with different concentrations of Cd inside the same film occurs. The presence of CdO in annealed Zn1-xCdxO films with the higher Cd content was confirmed by Raman spectra of cubic CdO nanoinclusions. The XRD data also revealed phase segregation of cubic CdO in annealed Zn1-xCdxO films (Tann = 600 °C) for x ⟩ 0.013.

Keywords:Zn1–xCdxO films, XRD, XPS, Raman spectroscopy, photoluminescence, phase segregation.

Manuscript received 07.03.14; revised version received 27.06.14; accepted for publication 16.09.14; published online 30.09.14.

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