A Multi-topic International Conference
UNCC_Honet logo_HONET    
11th HONET-PfE
Charlotte, North Carolina, USA
December 15 - 17, 2014 
Dr. Arshad Mahmood,
Project Director, Nano- devices Labs
NILOP/PIEAS,Islamabad, Pakistan                  
Email: drarshadjanjua@gmail.com

Title: Implantation Effets of transition metal in GaN Epitaxial Films prepared by RF-plasma assited MBE.


Group III-Nitride semiconductors are recognized as most promising materials for their applications in electronics and optoelectronics devices. In this regard, III-Nitrides based dilute magnetic semiconductors (DMSs) are also thought to be ideal materials for spintronic devices.
   In this work, epitaxial growth of gallium nitride (GaN) films on c-plane sapphire was done by radio frequency plasma assisted molecular beam epitaxy (RF-PAMBE). To achieve good quality epitaxial films, nitridation and aluminum nitride (AlN) buffer layers were grown in order to overcome the lattice mismatch. These processes were monitored during growth using reflection high-energy electron diffraction (RHEED) technique. The growth parameters such as substrate temperature and III/N ratio were optimized in all these processes. The growth mode transition from 3D to 2D has been observed, while changing both the substrate temperature and N/Ga ratio.
   GaN based diluted magnetic semiconductor (DMS) was fabricated by implanting Cu+ and Cr+ ions into GaN thin films at various ion fluxes. The structural, optical and magnetic characterization of the samples was performed through various diagnostic techniques. Incorporation of the implanted ions into the samples was confirmed by RBS, while XRD and Raman results revealed that no new phase was formed as a result of ion implantation, which suggested that implanted ions dissolved in matrix films by occupying interstitial and/or substitutional sites.
   FC/ZFC measurements indicated that the ferromagnetic effect was not related with super-paramagnetic phase formation. Our results indicate that both Cr and Cu ions implanted GaN and AlN films are true dilute magnetic semiconductors (DMS). The observed ferromagnetism in our samples does not originate from the clusters or secondary phases of TMs in the host semiconductor. Based on our analysis, it is concluded that strong p-d hybridization between TM atoms and N atoms in (TM) N4 tetrahedral configuration is responsible for the appearance of long range spin exchange coupling between TM atoms.

Short Biography:

Dr. Arshad Mahmood is a Professor and head of the Department of Materials Science at National Institute of Lasers and Optronics Pakistan/PIEAS. He received M.Sc. and M.Phil. degree from Quaid-e-Azam University, Islamabad Pakistan. After M. Phil, he actively participated in research for the development of superconductors. He received his Ph.D. in Materials Science and Engineering from the Autonomous University of Mexico in 2000.
  After his Ph.D. he joined NILOP, PIEAS University, Islamabad Pakistan, and received a research grant of US$ 3.0 million research and development in group III-Nitride semiconductors. Under this program, he has not only achieved several landmarks but also established six state of the art labs and groups which include

1. Simulations and design of group III-Nitride semiconductors devices,
2. Thin-films- and epitaxial- growth Lab,
3. Advanced material characterization Lab,
4. Lithography Lab,
5. Nano-Science Energy Lab,
6. Solar-cells Lab.

In addition he has made numerous contributions in the indigenous development of several systems including Reactive Magnetron Sputtering (DC/RF RMS) system, Reactive Pulsed Laser Ablation (RPLD) technique, multi pocket e-beam evaporation systems and so on. Professor Arshad Mahmood supervised several M.S and Ph.D students and is the author of more than 60 international publications.

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