Understanding phase separation in ZnCdO by a combination of structural and optical analysis

Galeckas, Augustinas; Trunk, Mareike; Zhang, Tianchong; Azarov, Alexander; Kuznetsov, A. Yu.

doi:10.1103/physrevb.83.125315

Cited by 58 publications

(39 citation statements)

References 52 publications

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“…At higher Cd concentrations, due to the different crystallographic structures, phase separation occurs, where both wz and zb phases (0.07 < x < 0.17) and wz, zb and rs phases (0.17 < x < 0.60) coexist (see Fig. 2.4) [24].…”

Section: Band Gap Engineeringmentioning

confidence: 99%

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Deep level related photoluminescence in ZnMgO

Trunk

Venkatachalapathy

Galeckas

et al. 2010

Applied Physics Letters

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Zinc oxide (ZnO) has been used in a wide range of products for many years, including, among others, varistors, surface acoustic wave devices and cosmetics. Besides these established applications, ZnO and its ternary alloys are now also being considered as potential materials for optoelectronic applications, such as light emitting diodes, photovoltaics, sensors, displays, etc. Unlike other materials, which could be used alternatively, ZnO has the advantage of being inexpensive, chemically stable and relatively plentiful. In spite of the long research history, fabrication of defect free ternary alloys and stable p-type ZnO is still challenging. The aim of this work was therefore to provide a better understanding of ZnO ternary alloys, so that -based on the gained knowledge -their optical properties can be further improved and, in a second step, optoelectronic applications based on these materials can soon be commercialized. The work carried out in this thesis was two-fold: the first part aimed at identifying the origin of defect related luminescence phenomena in ZnMgO, and the second part was dedicated to the exploration of a novel ZnCdO-based heterostructure photovoltaic applications.In the case of ZnMgO, luminescence properties of deep level defects were studied by photoluminescence (PL) spectroscopy and a model was proposed to explain the changes in the deep band emission with increasing Mg content. In this model, the observed trends can be understood by considering interaction of native zinc and oxygen defects of the ZnO sublattice with Mg interstitials (Mg i ). In summary, the deep level bands at 3.0 and 2.8 eV, which show a blueshift with increasing Mg content, were assigned to free-to-bound type transitions between zinc interstitials (Zn i ) with the valence band edge and between the conduction band edge with zinc vacancies (V Zn ), respectively. A red band at 2.0 eV, which does not show an apparent shift of the peak energy for increasing Mg content, is associated with the oxygen vacancies (V O ). Two luminescence bands at 2.3 and 2.5 eV, which are redshifted for higher Mg concentrations, were assigned to transitions between zinc and oxygen interstitials and between zinc interstitials and zinc vacancies, respectively. The redshift is interpreted in terms of a competing supply of electrons from slightly deeper Mg i donor states. The ZnMgO band gap diagram, which the model is based on, has contributed to gain valuable information about the nature of the deep defects both in ZnO and ZnMgO and is therefore of fundamental interest.In the second part of this work, focused on ZnCdO, a stacked heterostructure was designed for iii iv Abstract application in a photoelectrochemical cell, which is used for hydrogen production by photoelectrolysis using the semiconductor as an absorber. Optical and photoelectrochemical measurements led to the conclusion that the optical emission band for the ZnCdO heterostructures is broadened compared to a ZnO single layer. The broadened emission could be explained by combined ...

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Section: Band Gap Engineeringmentioning

confidence: 99%

“…Once a deeper understanding of origin of the deep level bands in ZnMgO had been gained, the knowledge was extended further to the twin ternary alloy ZnCdO. Controlled growth of single film ZnCdO by MOVPE could be achieved [24], making synthesis of ZnCdO-based photoelectrodes and possible:…”

Section: Band Gap Model For Deep Level Defects In Znmgomentioning

confidence: 99%

Deep level related photoluminescence in ZnMgO

Trunk

Venkatachalapathy

Galeckas

et al. 2010

Applied Physics Letters

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“…In particular, ternary Cd x Zn 1 x O alloys allow band-gap engineering in a wide range that covers the UV-yellow spectral region [2]. However, ZnO and CdO have different crystalline structures, wurtzite and rock salt, respectively, being difficult to stabilize a wurtzite phase of Cd x Zn 1 x O, which frequently results in phase separation [7,8]. The solubility of CdO in ZnO, besides being low, depends strongly on the growth conditions and technique that is used.…”

Section: Case Studiesmentioning

confidence: 99%

Nanostructures and thin films of transparent conductive oxides studied by perturbed angular correlations

Barbosa

Gonçalves

Redondo-Cubero

et al. 2013

Physica Status Solidi (b)

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The versatility of perturbed angular correlations (PAC) in the study of nanostructures and thin films is demonstrated, namely for the specific cases of ZnO/CdxZn1−xO thin films and Ga2O3 powder pellets and nanowires, examples of transparent conductive oxides. PAC measurements as a function of annealing temperature were performed after implantation of 111mCd/111Cd (T1/2 = 48 min) and later compared to density functional theory simulations. For ZnO, the substitution of Cd probes at Zn sites was observed, as well as the formation of a probe‐defect complex. The ternary CdxZn1−xO (x = 0.16) showed good macroscopic crystal quality but revealed some clustering of local defects around the probe Cd atoms, which could not be annealed. In the Ga2O3 samples, the substitution of the Cd probes in the octahedral Ga‐site was observed, demonstrating the potential of ion‐implantation for the doping of nanowires.

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“…alloy have a stable single-phase wz structure at x < 0.02, while at the higher Cd content (0.07 < x < 0.17), phase separation by wz, zb and rs structural phases occurs [5]. The Cd-rich and Cd-poor nanodomains were observed in microscopic cathodoluminescence spectra of O Cd Zn x x 1 epilayers with the higher Cd content [6].…”

Section: Introductionmentioning

confidence: 81%