Optical Properties of ZnCoO Films and Nanopowders

Abstract

ZnCoO is one of the most studied and promising semiconductor materials for spintronics applications. In this work we discuss optical and electrical properties of ZnCoO films and nanoparticles grown at low temperature by either atomic layer deposition or by a microwave driven hydrothermal method. We report that doping with cobalt quenches a visible photoluminescence of ZnO. We could observe a visible photoluminescence of ZnO only for samples with very low Co fractions (up to 1%). Mechanisms of photoluminescence quenching in ZnCoO are discussed. We also found that ZnO films remained n-type conductive after doping with Co, indicating that a high electron concentration and cobalt 2+ charge state can coexist.

Cathodoluminescence Profiling for Checking Uniformity of ZnO and ZnCoO Thin Films

“…Unfortunately, the method has its drawbacks -the test samples must be of a good quality (good emitters), and the level of impurities cannot exceed a few percent, otherwise CL emission is totally quenched [4,5].…”

“…ZnCoO films obtained by atomic layer deposition (ALD) are investigated with a scanning electron microscope (SEM) (surface topography), energy dispersive X-rays spectroscopy (EDS) (elements distribution) and cathodoluminescence (CL). In the latter method we utilize the fact that TM ions, such as manganese and cobalt, quench visible light emission of ZnO [4,5]. EDS resolution is about 1 µm, which is much larger than CL in-plane resolution of about 50-100 nm for a GaN [6] and also ZnO, which is determined by diffusion length of secondary electrons [6].…”

Microwave-Assisted Hydrothermal Synthesis of Co-Doped ZnO Nanoparticles for Water Oxidation Electrocatalysis

“…In this study, we have aimed to furnish OER surface catalytic sites by doping Co(II) ions into nanocrystals of zinc oxide (ZnO) that is expected to act as chemically stable and highly conductive host matrix. Doping of Co(II) ions into ZnO has actually been tried in many ways with an interest to realize ferromagnetic semiconductors for spintronic devices (21), by taking methods such as chemical vapor deposition (CVD) (22), sol-gel reaction (23), atomic layer deposition (ALD) (24), pulsed laser deposition (25), decomposition of complex precursors (26) and solvothermal reaction (21). Basu et al succeeded in Co(II) doping up to about 10at% and reported the magnetic properties of the product, but their solvothermal synthesis demands use of organic solvents and a high reaction temperature (300ºC), although the reaction time could be significantly shortened by employing microwave radiation (21).…”

Optical properties of ZnCoO layers obtained by PLD method

“…ZnCoO films have been extensively studied in last years [31][32][33][34] because they exhibit high mobility, good optical transparency, good electrical conductivity, and can be produced at lower material cost. For better using various devices, optical properties of ZnCoO DMS have been a focus of study, for example in [35][36][37][38][39].…”