High Quality Growth of Cobalt Doped GaN Nanowires with Enhanced Ferromagnetic and Optical Response.

Mudassar Maraj,Ghulam Nabi,Khurram Usman,Wenhong Sun,Engui Wang,Wenwang Wei,Yukun Wang

doi:10.3390/ma13163537

Mudassar Maraj, Ghulam Nabi + Show 5 more

Open Access

https://doi.org/10.3390/ma13163537

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Abstract

Group III–V semiconductors with direct band gaps have become crucial for optoelectronic and microelectronic applications. Exploring these materials for spintronic applications is an important direction for many research groups. In this study, pure and cobalt doped GaN nanowires were grown on the Si substrate by the chemical vapor deposition (CVD) method. Sophisticated characterization techniques such as X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), Transmission Electron Microscopy (TEM), High-Resolution Transmission Electron Microscopy (HRTEM) and photoluminescence (PL) were used to characterize the structure, morphology, composition and optical properties of the nanowires. The doped nanowires have diameters ranging from 60–200 nm and lengths were found to be in microns. By optimizing the synthesis process, pure, smooth, single crystalline and highly dense nanowires have been grown on the Si substrate which possess better magnetic and optical properties. No any secondary phases were observed even with 8% cobalt doping. The magnetic properties of cobalt doped GaN showed a ferromagnetic response at room temperature. The value of saturation magnetization is found to be increased with increasing doping concentration and magnetic saturation was found to be 792.4 µemu for 8% cobalt doping. It was also depicted that the Co atoms are substituted at Ga sites in the GaN lattice. Furthermore N vacancies are also observed in the Co-doped GaN nanowires which was confirmed by the PL graph exhibiting nitrogen vacancy defects and strain related peaks at 455 nm (blue emission). PL and magnetic properties show their potential applications in spintronics.

Highlights

Pure and Co-doped GaN nanowires were synthesized by a facile chemical vapor deposition (CVD) technique in the horizontal tube furnace (HTF) as shown in the schematic diagram of Figure 1
The magnetic properties of Co-doped GaN nanowires with 2%, 4%, 6% and 8% were determined by vibrating sample magnetometer (VSM) at room temperature (RT)
The small shift in the X-ray diffraction (XRD) peaks proved the incorporation of Co into the GaN lattice which were in good agreement with the PL results

Summary

Introduction

The spintronics industry aims to develop devices that can manipulate the spin of the electron as an additional degree of freedom, thereby providing a novel kind of electronic device which is replacing the traditional electronic sensors, Light-emitting diode (LED) displays, memory devices etc. Since the prediction of room temperature ferromagnetism by Deitl, the semiconductors, doped with ferromagnetic ions, are considered to be one of the sources of ferromagnetism [1] These doped semiconductors are called dilute-magnetic semiconductors (DMSs) and have become important constituent of the spintronics industry. The GaN and ZnO-based diluted semiconductors (DMSs) with wide band gap characteristic properties, have gained considerable interest in theoretical predictions of ferromagnetism in these materials above room temperature. For the practical applications of these nanostructure materials in spintronics devices, they must exhibit ferromagnetism with a critical temperature above room temperature In this regard, the synthesis routes that grow high quality 1D structures, especially nanowires, are crucial to improve the morphology and physical properties. The enhanced magnetic properties ensure its applications for spintronics and the synthesis method employed here provides the route to obtain better morphology of these nanowires

Experimental Procedure

Magnetic Properties

Photoluminescenceofofpure pureand and cobalt cobalt doped

Findings

Conclusions