The influence of uniaxial stress on the electronic T13(F)→T23(F) transitions of Ni2+ (d8) in ZnO at 4216, 4240, and 4247 cm-1 is studied. It is shown that the split pattern and polarized properties of IR absorption lines are consistent with a dynamic Jahn-Teller effect in the T23(F) state of the defect. © 2013 Elsevier Ltd

Herklotz F.

Kutin Y.

Lavrov E.

Solid State Communications

Kazan Federal University Digital Repository

Effect of uniaxial stress on substitutional Ni in ZnOE.V. Lavrov a,n, F. Herklotz a, Y.S. Kutin ba Technische Universita¨t Dresden, 01062 Dresden, Germanyb Kazan Federal University, Federal Center of Shared Facilities, 420008 Kazan, Russiaa r t i c l e i n f oArticle history:Received 9 January 2013Accepted 21 January 2013by M. GrynbergAvailable online 29 January 2013Keywords:A. ZnOC. NiE. IR absorptionE. Uniaxial stressa b s t r a c tThe inﬂuence of uniaxial stress on the electronic 3T1ðFÞ-3T2ðFÞ transitions of Ni2þ (d8) in ZnO at 4216,4240, and 4247 cm1 is studied. It is shown that the split pattern and polarized properties of IRabsorption lines are consistent with a dynamic Jahn–Teller effect in the 3T2ðFÞ state of the defect.& 2013 Elsevier Ltd. All rights reserved.1. IntroductionZnO is a wide band gap (3.3 eV at 300 K) semiconductor whichregained much attention in the last decade due to many potentialapplications such as: a material for blue and UV light-emittingdiodes, radiation hard material, or a transparent highly conduct-ing oxide [1]. Because of theoretically predicted high Curietemperature, there is also considerable interest in the develop-ment of transition metal (Co, Mn, Fe, and Ni) doped ZnO-baseddiluted magnetic semiconductors [2–6].Nickel is a common impurity in ZnO, which is often unin-tentionally introduced into the material during the process ofcrystal growth. In photoluminescence (PL) and IR absorption, Niresults in a number of features. In particular, the 4T2ðFÞ-4A2ðFÞtransitions of the Ni3þ (d7) ion can be seen in PL spectra at 6090.5and 6096.2 cm1 [7]. The 3T1ðFÞ-3T2ðFÞ transitions of Ni2þ (d8)are observed in IR absorption at 4216, 4240, and 4247 cm1 [7,8],whereas the 8340 cm1 line was associated with the3T1ðFÞ-3A2ðFÞ transition [8]. Recently, it was shown that thisband reveals a substructure associated with the main 58Ni, 60Ni,and 62Ni isotopes, thus conﬁrming the microscopic origin of thedefect [9].Piezospectroscopy provides defect symmetries and yields valuesfor stress shift rates including hydrostatic shift rates [10–12]. InZnO, piezospectroscopic studies have been recently applied to studynumerous hydrogen- and copper-related defects [13–15].Here we report the results of a uniaxial stress study of Niperformed on the 3T1ðFÞ-3T2ðFÞ transitions at 4216, 4240, and4247 cm1.2. Experimental detailsZnO samples used for uniaxial stress measurements in thepresent study were hydrothermally grown n-type substrates sup-plied by CrysTec GmbH. The dimensions of the samples uninten-tionally doped with Ni were around 621 mm3. The uniaxialstress was applied along the longest side of the samples, whichwere cut parallel to c, ½1210, or ½1010. Intentional doping with Niwas performed on ZnO grown from the vapor phase at the Institutefor Applied Physics, University of Erlangen (Germany) [16].Measurements were performed up to around 0.3 GPa at 8–10 K with a home-built stress rig that was mounted in a He gasﬂow cryostat equipped with ZnSe windows. The stress wassupplied to samples by a pneumatic cylinder and transferred viaa push rod. Polarized spectra were obtained using a wire-gridpolarizer with a KRS-5 substrate.Infrared absorption spectra were recorded with a BomemDA3.01 Fourier transform spectrometer equipped with a globarlight source, a CaF2 beam splitter, and a liquid-nitrogen-cooledInSb detector. The spectral resolution was 0.25 cm1.Photoluminescence measurements were carried out at 4.2 Kwith samples immersed into liquid helium in an Oxford cryostat.Excitation was performed by the 325 nm line of a HeCd laser withan excitation power of around 2 mW.3. Results and discussion3.1. Doping of ZnO with NiIn the literature, a number of IR absorption and PL lines havebeen attributed to different transition metals embedded in ZnO[7,8,17–19]. Recently, Vlasenko et al. have shown that the sharpContents lists available at SciVerse ScienceDirectjournal homepage: www.elsevier.com/locate/sscSolid State Communications0038-1098/$ - see front matter & 2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.ssc.2013.01.021n Corresponding author. Tel.: þ49 351 463 33637; fax: þ49 351 463 37060.E-mail address: edward.lavrov@physik.tu-dresden.de (E.V. Lavrov).Solid State Communications 159 (2013) 36–40

Effect of uniaxial stress on substitutional Ni in ZnO

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Effect of uniaxial stress on substitutional Ni in ZnO

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