Effect of Mn concentration on the structural, optical, and magnetic properties of GaMnN

Thaler, G. T.; Frazier, R. M.; Gila, B. P.; Stapleton, J.; Davidson, Mark R.; Abernathy, C. R.; Pearton, S. J.; Segre, Carlo U.

doi:10.1063/1.1649819

Cited by 59 publications

(47 citation statements)

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“…Em particular, materiais como Ga 1-x Mn x As e In 1-x Mn x As apresentam desvantagem de suas temperaturas de Curie encontrarem-se abaixo da temperatura ambiente, Tc ~ 100 K e Tc ~ 50 K, respectivamente, tornando-os menos convenientes para uso prático. 5,6,14 Outros materiais que também apresentaram propriedades ferromagnéticas à temperatura ambiente são o TiO 2 e ZnO, dopados com Mn, Fe e Co. [15][16][17][18] Para crescer filmes de Ga 1-x Mn x N (GaMnN) encontramos técni-cas como a Epitaxia por Feixe Molecular (MBE), a qual tem como principal característica o controle do crescimento dos filmes a nível de camadas atômicas, podendo produzir filmes monocristalinos com baixa densidade de defeitos. No entanto, para conseguir certas concentrações de Mn sem que ocorra segregação desse elemento faz-se necessário o uso de temperaturas mais baixas que as ideais para a preparação do GaN, 14 de maneira que os materiais podem apresentar grandes quantidades de defeitos.…”

Section: Introductionunclassified

Efeitos da adição de átomos de Mn na rede do GaN via métodos de estrutura eletrônica

Mazini¹,

Cavalheiro

Leite³

et al. 2010

Quím. Nova

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Recebido em 6/5/09; aceito em 9/11/09; publicado na web em 10/3/10 INDIRECT EFFECTS OF THE Mn INCORPORATION ON THE ELECTRONIC STRUCTURE OF NANOCRYSTALLINE GaN.A computational method to simulate the changes in the electronic structure of Ga 1-x Mn x N was performed in order to improve the understanding of the indirect contribution of Mn atoms. This periodic quantum-mechanical method is based on density functional theory at B3LYP level. The electronic structures are compared with experimental data of the absorption edge of the GaMnN. It was observed that the indirect influence of Mn through the structural parameters can account for the main part of the band gap variation for materials in the diluted regime (x<0.08), and is still significant for higher compositions (x~0.18).Keywords: GaN; diluted magnetic semiconductor (DMS); DFT. INTRODUÇÃOEstudos recentes mostraram que materiais como GaAs, InAs e GaN, dopados com quantidades de Mn, Fe, Ni, Co, 1-8 da ordem de 5% apresentam, além das propriedades semicondutoras, propriedades ferromagnéticas. 5,9 As propriedades magnéticas destes materiais estão associadas ao fato de que, nos metais de transição citados, os níveis d estão incompletos e apresentam geralmente um valor elevado de momento magnético. Isto confere aos materiais propriedades de semicondutor magnético diluído (DMS).Os DMSs são potenciais candidatos para utilização em spintrô-nica, tecnologia na qual os benefícios da carga e do spin do elétron se unem em um único dispositivo, 7 por possibilitarem a injeção de correntes elétricas com alto grau de polarização de spin entre um metal e um semicondutor que é observada em junções metal semicondutor tradicional.3,10-12 Os dispositivos spintrônicos baseados em DMSs apresentam potencial para promover a integração entre comunicação, memória e processamento em um único dispositivo proporcionando ganho extraordinário na velocidade de processamento de dados. 3,4,7,13 Outro benefício dos dispositivos spintrônicos reside na grande economia de energia, quando comparada aos dispositivos tradicionais. 5Entre os DMSs conhecidos o GaN dopado com Mn é um dos mais promissores candidatos a utilização em dispositivos spintrô-nicos, pois este material pode apresentar uma temperatura de Curie (Tc) acima da temperatura ambiente (Tc ~ 400 K). Em particular, materiais como Ga 1-x Mn x As e In 1-x Mn x As apresentam desvantagem de suas temperaturas de Curie encontrarem-se abaixo da temperatura ambiente, Tc ~ 100 K e Tc ~ 50 K, respectivamente, tornando-os menos convenientes para uso prático. 5,6,14 Outros materiais que também apresentaram propriedades ferromagnéticas à temperatura ambiente são o TiO 2 e ZnO, dopados com Mn, Fe e Co. [15][16][17][18] Para crescer filmes de Ga 1-x Mn x N (GaMnN) encontramos técni-cas como a Epitaxia por Feixe Molecular (MBE), a qual tem como principal característica o controle do crescimento dos filmes a nível de camadas atômicas, podendo produzir filmes monocristalinos com baixa densidade de defeitos. No entanto, para conseguir certas concentrações de Mn...

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Section: Introductionunclassified

Efeitos da adição de átomos de Mn na rede do GaN via métodos de estrutura eletrônica

Mazini¹,

Cavalheiro

Leite³

et al. 2010

Quím. Nova

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“…1,2 The Curie temperature above 300 K and the increasing interest and control of the ferromagnetism are among the advantages of focusing on the properties of this material. The success of the preparation of ferromagnetic Ga 1−x Mn x N using the molecular beam epitaxy ͑MBE͒ technique is quite recent [3][4][5][6][7] and has attracted the attention of several groups concerning the mentioned as well as other techniques. [8][9][10][11][12][13][14] In a recent report we have described the preparation of Ga 1−x Mn x N nanocrystalline films using the sputtering technique.…”

Section: Introductionmentioning

confidence: 99%

Structural and vibrational analysis of nanocrystalline Ga1−xMnxN films deposited by reactive magnetron sputtering

Silva

Leite

Tabata

et al. 2007

Journal of Applied Physics

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The structural and vibrational properties of nanocrystalline Ga 1−x Mn x N films deposited by reactive magnetron sputtering were analyzed in a wide composition range ͑0 Ͻ x Ͻ 0.18͒. The films were structurally characterized using x-ray diffraction with Rietveld refinement. The corresponding vibrational properties were investigated using micro-Raman and Fourier transform infrared spectroscopies. The films present a high crystallized fraction, crystallites having wurtzite structure, and high orientation texture with the c axis oriented perpendicular to the substrate surface. Rietveld analysis indicates that Mn atoms are incorporated substitutionally into Ga positions and show that the ionic character of cation-N bonds along the c axis is favored by the Mn incorporation. No evidence for Mn segregation or Mn rich phases was found in the composition range analyzed. Micro-Raman scattering spectra and infrared absorption experiments showed progressive changes with the increase of x and monotonic shifts of the GaN TO and LO peaks to lower frequencies. The structural and vibrational analyses are compared and the influence of Mn on the static and dynamic properties of the lattice is analyzed.

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“…A similar trend is found in Mn-doped GaN that has been attributed to the incorporation of substitutional impurities on the group-III site. 8 Figure 2 Fig. 2(c).…”

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confidence: 99%

Observation of ferromagnetism above 900K in Cr–GaN and Cr–AlN

Liu

Singh

et al. 2004

Applied Physics Letters

211

110

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(ReceivedWe report ferromagnetism at over 900 K in Cr-GaN and Cr-AlN thin films. The magnetic properties vary as a function of Cr concentration with 60%, and 20%, of the Cr being magnetically active at 3% doping in GaN, and 7% in AlN, respectively. In the GaN sample with the highest magnetically active Cr (60%), channeling Rutherford Backscattering indicates that over 70% of Cr impurities are located on substitutional sites. These results give indisputable evidence that substitutional Cr defects are involved in the magnetic behavior. While Cr-AlN is highly resistive, Cr-GaN exhibits properties characteristic of hopping conduction including T 1/2 resistivity dependence and small Hall mobility (0.06 cm 2 /V . s). A large negative magnetoresistance is attributed to the influence of the magnetic field on the quantum interference between the many paths linking two hopping sites. The results strongly suggest that ferromagnetism in Cr-GaN and Cr-AlN can be attributed to the double exchange mechanism as a result of hopping between near-midgap substitutional Cr impurity bands. Cr-GaN, 5 and Cr-AlN. 6 (Ga,Mn)N films grown by molecular beam epitaxy were reported to be ferromagnetic above room temperature, with a Curie temperature, T c , of 940 K. 7 Another study of the same system synthesized using solid-state diffusion reported a T c in the range of 220-370 K, 3 while bulk Cr-doped GaN fabricated using the sodium flux method was reported to have a T c of 280 K. 5 The search for the physical mechanism responsible for the observed ferromagnetic properties and the question of the applicability of the classical magnetic models have become topics of intense interest. This letter reports the observation of ferromagnetism in Cr-GaN and Cr-AlN above 900 K, and describes the structural, electrical and magnetic properties of the materials.The Cr-GaN and Cr-AlN films were grown on 6H-SiC (0001) and sapphire (0001) substrates in a reactive molecular beam epitaxy system. Structural properties were characterized using X-ray diffraction ( Magnetic fields were applied parallel to the film plane during susceptibility measurements and perpendicular to the film during magnetoresistance (MR) measurements. The diamagnetic background contributions originating from the substrate and the sample holder were subtracted

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Effect of Mn concentration on the structural, optical, and magnetic properties of GaMnN

Abstract: Structural and magnetic properties of (Ga,Mn)N layers grown on SiC by reactive molecular beam epitaxy

Cited by 59 publications

References 25 publications

Efeitos da adição de átomos de Mn na rede do GaN via métodos de estrutura eletrônica

Efeitos da adição de átomos de Mn na rede do GaN via métodos de estrutura eletrônica

Structural and vibrational analysis of nanocrystalline Ga1−xMnxN films deposited by reactive magnetron sputtering

Observation of ferromagnetism above 900K in Cr–GaN and Cr–AlN

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