TY - JOUR

T1 - Self-Healing of Defect-Mediated Disorder in ZnO Thin Films Grown by Atomic Layer Deposition

AU - Benny, Don P.

AU - Munya, Vikas

AU - Ghosh, Arpan

AU - Kumar, Ravinder

AU - Pal, Dipayan

AU - Pfnür, Herbert

AU - Chattopadhyay, Sudeshna

N1 - Funding Information: We would like to acknowledge IIT Indore for all kinds of support for this work, the FESEM facility of IISER-Pune, and the Nanoscale Research Facility (NRF) at IIT Delhi for the PL measurements. This work is partially supported by the Science and Engineering Research Board (SERB), India Project No. CRG/2020/005595. We acknowledge support by the Deutsche Akademischer Austauschdienst (DAAD) who funded the project under “A New Passage to India” programme between Leibniz Universität Hannover and the Indian Institute of Technology Indore. V. M. is thankful to CSIR-UGC, New Delhi under the UGC-Ref. No. 1364/(CSIR-UGC NET JUNE 2018) and R. S. is thankful to DST-INDIA, New Delhi under the Award No. IF190536 for providing the fellowships.

PY - 2023/12

Y1 - 2023/12

N2 - Electronics with semiconductors rely strongly on defect concentrations and on the properties of these defects. Here we study ZnO thin films which were grown by atomic layer deposition. An interesting mechanism of build-up and of self-healing of Zn interstitial defects as a function of layer thickness d was found, based on measurements of photoabsorption (PA), photoluminescence (PL) and x-ray diffraction as a function of d. The concentration of Zn interstitial defects increases up to d = 19 nm, coupled with a corresponding increase of the Urbach energy, Eu, in PA. At this layer thickness, the growth mode changes from the formation of a homogeneous layer to a layer of nano-crystals, where the nano-crystals grow in size with d. Surprisingly, the Zn interstitial concentration decreases spontaneously once the layer thickness exceeds d = 38 nm. We explain this behavior by a reduction of diffusion barriers for Zn interstitials as a function of average ZnO particle size leading to spontaneous diffusion to the particle surface and subsequent oxidation therein. At the same time, the concentration of oxygen vacancies, mostly located at the particle surface, is greatly reduced with increasing film thickness. The study is of importance in designing opto- and nano-electronic devices by means of appropriate selection of ZnO film thickness, for targeted quality, property and further practical applications. Graphical Abstract: [Figure not available: see fulltext.].

AB - Electronics with semiconductors rely strongly on defect concentrations and on the properties of these defects. Here we study ZnO thin films which were grown by atomic layer deposition. An interesting mechanism of build-up and of self-healing of Zn interstitial defects as a function of layer thickness d was found, based on measurements of photoabsorption (PA), photoluminescence (PL) and x-ray diffraction as a function of d. The concentration of Zn interstitial defects increases up to d = 19 nm, coupled with a corresponding increase of the Urbach energy, Eu, in PA. At this layer thickness, the growth mode changes from the formation of a homogeneous layer to a layer of nano-crystals, where the nano-crystals grow in size with d. Surprisingly, the Zn interstitial concentration decreases spontaneously once the layer thickness exceeds d = 38 nm. We explain this behavior by a reduction of diffusion barriers for Zn interstitials as a function of average ZnO particle size leading to spontaneous diffusion to the particle surface and subsequent oxidation therein. At the same time, the concentration of oxygen vacancies, mostly located at the particle surface, is greatly reduced with increasing film thickness. The study is of importance in designing opto- and nano-electronic devices by means of appropriate selection of ZnO film thickness, for targeted quality, property and further practical applications. Graphical Abstract: [Figure not available: see fulltext.].

KW - Atomic layer deposition

KW - defect-induced disorder

KW - morphology

KW - photoluminescence

KW - thickness-dependent optical properties

KW - Urbach energy

KW - ZnO thin-film

UR - http://www.scopus.com/inward/record.url?scp=85173854800&partnerID=8YFLogxK

U2 - 10.1007/s11664-023-10758-3

DO - 10.1007/s11664-023-10758-3

M3 - Article

AN - SCOPUS:85173854800

VL - 52

SP - 8293

EP - 8302

JO - Journal of electronic materials

JF - Journal of electronic materials

SN - 0361-5235

IS - 12

ER -