Journal of Crystal Growth 285 (2005) 300–311 Room temperature ferromagnetism in CrGaN: Dependence on growth conditions in rf N-plasma molecular beam epitaxy Muhammad B. Haider a , Rong Yang a , Hamad Al-Brithen a , Costel Constantin a , David C. Ingram a , Arthur R. Smith a,Ã , Gabriel Caruntu b , Charles J. O’Connor b a Condensed Matter and Surface Science Program, Department of Physics and Astronomy, Ohio University, Athens, OH 45701, USA b Advanced Materials Research Institute, University of New Orleans, New Orleans, LA 70148, USA Received 18 June 2004; received in revised form 2 June 2005; accepted 29 August 2005 Communicated by C.R. Abernathy Abstract Here, we report the influence of the growth conditions for CrGaN grown with the N-polarity on sapphire (0 0 0 1) using radio frequency N plasma-assisted molecular beam epitaxy. Samples are grown under different Ga/N flux ratio of 0.65–1.0 at substrate temperatures of 650 and 700  C. The Cr/Ga flux ratio is set to either 3% or 5%. These growth parameters allow to vary over a range of growth conditions from N-rich to Ga-rich. It is shown that the surface condition during growth influences the surface morphology and magnetic properties of CrGaN. In particular, we show that N-rich and metal-rich growth conditions result in room temperature ferromagnetism. Also discussed are the influence of Cr on the surface reconstruction and also the influence of annealing on the properties of the CrGaN film. r 2005 Elsevier B.V. All rights reserved. PACS: 75.50.Pp; 81.15.Hi; 61.10.Nz; 61.14.Hg Keywords: A1. AFM; A1. RHEED; A1. XRD; A3. MBE; B1. GaN; B2. DMS 1. Introduction Many studies have been performed recently for dilute magnetic semiconductors (DMS) due to their potential use in spintronics applications. Recent theoretical studies have predicted that nitride diluted magnetic semiconductors (NDMS) can exhibit ferromagnetism above room tempera- ture [1,2]. According to Sato et al., based on first- principles calculations in the mean field approx- imation, CrGaN has a stable ferromagnetic state even with a Cr concentration as high as 25% [2]. There are a number of reports about the growth and near or above room temperature ferromag- netism for CrGaN [3–6]. Lee et al. reported ARTICLE IN PRESS www.elsevier.com/locate/jcrysgro 0022-0248/$ - see front matter r 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jcrysgro.2005.08.047 Ã Corresponding author. Tel.: +1 7405972964; fax: +1 7405930433. E-mail addresses: haider@helios.phy.ohiou.edu (M.B. Haider), smitha2@ohio.edu (A.R. Smith).