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1.
We have grown MnxGe1−x films (x=0, 0.06, 0.1) on Si (001) substrates by magnetron cosputtering, and have explored the resulting structural, morphological, electrical and magnetic properties. X-ray diffraction results show there is no secondary phase except Ge in the Mn0.06Ge0.94 film while new phase appears in the Mn0.1Ge0.9 film. Nanocrystals are formed in the Mn0.06Ge0.94 film, determined by field-emission scanning electron microscopy. Hall measurement indicates that the Mn0.06Ge0.94 film is p-type semiconductor and hole carrier concentration is 6.07×1019 cm−3 while the MnxGe1−x films with x=0 has n-type carriers. The field dependence of magnetization was measured using alternating gradient magnetometer, and it has been indicated that the Mn0.06Ge0.94 film is ferromagnetic at room temperature. 相似文献
2.
Weixia Gao Li WangDenglu Hou Yuchan HuQian Zhang Li MaCongmian Zhen 《Applied Surface Science》2011,257(21):8871-8875
Ge1−xMnx (x = 0, 0.013, 0.0226, 0.0339, 0.0565, 0.0678, 0.0904, 0.113) films prepared by magnetron sputtering at 773 K had a Ge cubic structure except for x = 0.1130. Co ion implantation into these films can effectively prevent the formation of a second phase. Both single-doped and co-doped samples were ferromagnetic at room temperature. The d-d exchange interaction between the interstitial Mn (MnT) and the substituted Mn (MnGe) resulted in ferromagnetism in the sputtered films. Since Co ion implantation destroyed the MnT-MnGe-MnT complex, the saturated magnetization decreased. Hall measurements revealed that the Co ion implanted films were n-type semiconductors, and the anomalous Hall Effect (AHE) suggested the ferromagnetism was carrier-mediated in the implanted films. 相似文献
3.
(Ga1−xMnx)N thin films grown on GaN buffer layers by using molecular beam epitaxy were investigated with the goal of producing diluted magnetic semiconductors (DMSs) with band-edge exciton transitions for applications in optomagnetic devices. The magnetization curve as a function of the magnetic field at 5 K indicated that ferromagnetism existed in the (Ga1−xMnx)N thin films, and the magnetization curve as a function of the temperature showed that the ferromagnetic transition temperature of the (Ga1−xMnx)N thin film was above room temperature. Photoluminescence and photoluminescence excitation spectra showed that band-edge exciton transitions in (Ga1−xMnx)N thin films appeared. These results indicate that the (Ga1−xMnx)N DMSs with a magnetic single phase hold promise for potential applications in spin optoelectronic devices in the blue region of the spectrum. 相似文献
4.
Thin films of Ge100−xFex (x in at%) alloys, fabricated by thermal co-evaporation, have an amorphous structure at compositions x<∼40, although an unidentified crystalline phase with an FCC symmetry also exists at low Fe content. Magnetization versus temperature curves show that saturation magnetization is non-zero (1 to 2.5 emu/cm3) and remains nearly unchanged up to the highest measured temperature of 350 K. Magnetic hysteresis loops at room temperature show a typical ferromagnetic shape, complete saturation occurring by 1–2 kOe. These results may indicate ferromagnetic ordering at room temperature. No definite tendency is observed in the compositional dependence of saturation magnetization. 相似文献
5.
We report on the ferromagnetic characteristics of Zn1−xMnxO films (x=0.1-0.3) prepared by the sol-gel method on silicon substrates using transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffractometry (XRD) and superconducting quantum interference device (SQUID) magnetometry at various temperatures. Magnetic measurement show that the Curie temperature (TC) and the coercive field (HC) were ∼39 K and ∼2100 Oe for the film of x=0.2, respectively. EDS and TEM measurements indicate that Mn content at the interface is significantly higher than that at the center of the Zn0.8Mn0.2O film showing the ratio, Zn:Mn:O≅1:12:15. This experimental evidence suggests that ferromagnetic precipitates containing manganese oxide may be responsible for the observed ferromagnetic behavior of the film. 相似文献
6.
Sang Soo Yu Kyung Hee Han Young Eon Ihm Dojin Kim Hyojin Kim Chang Soo Kim Hyun Ryu Sangjun Oh 《Journal of magnetism and magnetic materials》2006
Amorphous Ge1−xCrx thin films are deposited on (1 0 0)Si by using a thermal evaporator. Amorphous phase is obtained when Cr concentration is lower than 30.7 at%. The electrical resistivities are 1.89×10−3–0.96×102 Ω cm at 300 K, and decrease with Cr concentration. The Ge1−xCrx thin films are p-type. The hole concentrations are 5×1016–7×1021 cm−3 at 300 K, and increase with Cr concentration. Magnetizations are 7.60–1.57 emu/cm3 at 5 K in the applied field of 2 T. The magnetizations decrease with Cr concentration and temperature. Magnetization characteristics show that the Ge1−xCrx thin films are paramagnetic. 相似文献
7.
R.C. Teixeira I. Doi J.A. Diniz J.W. Swart M.B.P. Zakia 《Applied Surface Science》2007,254(1):207-212
This paper investigates the structure and surface characteristics, and electrical properties of the polycrystalline silicon-germanium (poly-Si1−xGex) alloy thin films, deposited by vertical reduced pressure CVD (RPCVD) in the temperature range between 500 and 750 °C and a total pressure of 5 or 10 Torr. The samples exhibited a very uniform good quality films formation, with smooth surface with rms roughness as low as 7 nm for all temperature range, Ge mole fraction up to 32% (at 600 °C), textures of 〈2 2 0〉 preferred orientation at lower temperatures and strong 〈1 1 1〉 at 750 °C, for both 5 and 10 Torr deposition pressures. The 31P+ and 11B+ doped poly-Si1−xGex films exhibited always lower electrical resistivity values in comparison to similar poly-Si films, regardless of the employed anneal temperature or implantat dose. The results indicated also that poly-Si1−xGex films require much lower temperature and ion implant dose than poly-Si to achieve the same film resistivity. These characteristics indicate a high quality of obtained poly-Si1−xGex films, suitable as a gate electrode material for submicron CMOS devices. 相似文献
8.
S.K. BarikC. Krishnamoorthi R. Mahendiran 《Journal of magnetism and magnetic materials》2011,323(7):1015-1021
We have studied the effect of Fe substitution on magnetic and magnetocaloric properties in La0.7Sr0.3Mn1−xFexO3 (x=0.05, 0.07, 0.10, 0.15, and 0.20) over a wide temperature range (T=10-400 K). It is shown that substitution by Fe gradually decreases the ferromagnetic Curie temperature (TC) and saturation magnetization up to x=0.15 but a dramatic change occurs for x=0.2. The x=0.2 sample can be considered as a phase separated compound in which both short-range ordered ferromagnetic and antiferromagnetic phases coexist. The magnetic entropy change (−ΔSm) was estimated from isothermal magnetization curves and it decreases with increase of Fe content from 4.4 J kg−1 K−1 at 343 K (x=0.05) to 1.3 J kg−1 K−1 at 105 K (x=0.2), under ΔH=5 T. The La0.7Sr0.3Mn0.93Fe0.07O3 sample shows negligible hysteresis loss, operating temperature range over 60 K around room temperature with refrigerant capacity of 225 J kg−1, and magnetic entropy of 4 J kg−1 K−1 which will be an interesting compound for application in room temperature refrigeration. 相似文献
9.
Si1−xMnx diluted magnetic semiconductor (DMS) bulks were formed by using an implantation and annealing method. Energy dispersive X-ray fluorescence, transmission electron microscopy (TEM), and double-crystal rocking X-ray diffraction (DCRXD) measurements showed that the grown materials were Si1−xMnx crystalline bulks. Hall effect measurements showed that annealed Si1−xMnx bulks were p-type semiconductors. The magnetization curve as a function of the magnetic field clearly showed that the ferromagnetism in the annealed Si1−xMnx bulks originated from the interaction between interstitial and substitutional Mn+ ions, which was confirmed by the DCRXD measurements. The magnetization curve as a function of the temperature showed that the ferromagnetic transition temperature was approximately 75 K. The present results can help to improve understanding of the formation mechanism of ferromagnetism in Si1−xMnx DMS bulks. 相似文献
10.
Multiple stacked self-assembled (In1−xMnx)As quantum-dot (QD) arrays were grown on GaAs (100) substrates by using molecular-beam epitaxy with a goal of producing (In1−xMnx)As QDs with a semiconductor phase and a high ferromagnetic transition temperature (Tc). Atomic force microscopy, magnetic force microscopy, high-resolution transmission electron microscopy, and energy dispersive X-ray fluorescence measurements showed that crystalline multiple stacked (In0.84Mn0.16)As with symmetric single-domain particle were formed on GaAs substrates. Near-field scanning optical spectroscopy spectra at 10 K for the (In0.84Mn0.16)As multiple stacked QDs showed that the band-edge exciton transitions were observed. The magnetization curve as a function of the magnetic field at 5 and 300 K indicated that the multiple stacked (In0.84Mn0.16)As QDs were ferromagnetic, and the magnetization curve as a function of the temperature showed that the Tc was as high as 400 K. These results provide important information on the optical and magnetic properties for enhancing the Tc of (In1−xMnx)As-based nanostructures. 相似文献
11.
Ferromagnetic Ga1−xMnxAs layers (where x≈4.7–5.5%) were grown on (1 0 0) GaAs substrates by molecular beam epitaxy. These p-type (Ga,Mn)As films were revealed to have a ferromagnetic structure and ferromagnetism is observed up to a Curie temperature of 318 K, which is ascribed to the presence of MnAs secondary magnetic phases within the film. It is highly likely that the phase segregation occurs due to the high Mn cell temperature around 890–920 °C, as it is well established that GaMnAs is unstable at such a high temperature. The MnAs precipitate in the samples with x≈4.7–5.5% has a Curie temperature Tc≈318 K, which was characterized from field-cooled and zero-field-cooled magnetization curves. 相似文献
12.
Mei XuLihong Yang Youxia LiZhengang Guo Yaping ZhangHongmei Qiu Liqing Pan 《Physica B: Condensed Matter》2011,406(17):3180-3186
Nanoscale Cu1−xMnxO powder is prepared by using the combustion synthesis technique with two different fuels. The structural properties of the powder are determined using Rietveld refinement of X-ray diffraction data, high-resolution transmission electron microscopy, and Fourier transform infrared spectroscopy, while its magnetic properties are analyzed by means of hysteresis loop and temperature dependence of magnetization. The results show that (1) the Cu1−xMnxO nanocrystal is of monoclinic CuO structure, with grain size of 10-30 nm varying with the type of fuel, the nitrate/fuel ratio (N/F), and the Mn concentration, the doping of Mn has a little influence on the lattice parameters; (2) when the Mn concentration is higher than 7%, a small amount of impurity phase of CuMn2O4 appears and annihilates the potential cation vacancies; (3) all of the samples with x≥5% exhibit low-temperature ferromagnetism with the Curie temperature of ∼90 K, which increases slightly by raising the Mn concentration; (4) the paramagnetic moment per Mn ion is around 2-4 bohr magneton above the Curie temperature, which decreases with increasing Mn concentration, implying that the nearest Mn ions are antiferromagnetically coupled and the ferromagnetic order could originate from the super-exchange of next nearest Mn ions along the [1 0 1?] direction. 相似文献
13.
Younghun Hwang Sunglae ChoHyekyeong Kim Youngho Um 《Journal of magnetism and magnetic materials》2006
We have investigated the magnetic and electrical transport properties of Si1−xMnx single crystals grown by the vertical Bridgman method. The alloys with Mn concentrations up to x=0.64 have weak ferromagnetic ordering around TC∼30 K. However, Si0.25Mn0.75 alloys show weak ferromagnetic ordering at 70 K and antiferromagnetic ordering at 104 K, which is confirmed by magnetization and electrical transport studies. 相似文献
14.
N.P. Duong L.T. Hung T.D. Hien N.P. Thuy N.T. Trung E. Brück 《Journal of magnetism and magnetic materials》2007
A study of the half-metallic character of the semi Heusler alloys Co1−xCuxMnSb (0?x?0.9) is presented. We investigated the saturation magnetization MS at temperatures from 5 K to room temperature and the temperature dependence of the DC magnetic susceptibility χ above Curie temperature TC. The magnetic moments at 5 K, for most compositions are very close to the quantized value of 4 μB for Mn3+ ion, the compound with 90% Co substituted by Cu is still ferromagnetic with MS (5 K)=3.78 μB/f.u. These results emphasize the role of Co atoms in maintaining the ferromagnetic order in the material. The Curie temperature is decreased from 476 K to about 300 K as the Cu content increases from 0% to 90%. Above TC, the χ−1 vs T curves follow very well the Curie–Weiss law. The effective moment μeff and paramagnetic Curie temperature θ are derived. A comparison between the values of MS at 5 K and μeff shows a transition from localized to itinerant spin system in these compounds. 相似文献
15.
Sang Soo Yu Ki Hak Kim Young Eon Ihm Dojin Kim Hyojin Kim Soon Ku Hong Chang Soo Kim Hyun Ryu Sangjun Oh 《Journal of magnetism and magnetic materials》2006
Si1−xMnx (x?0.22) thin films were grown by using a thermal evaporator, and their magnetic and electrical properties were investigated. The Si1−xMnx semiconductors are amorphous when Mn concentration is 9.0 at% and less. The electrical resistivities of amorphous Si1−xMnx (x?0.09) semiconductor thin films are in the range of 9.86–6.59×10−4 Ω cm at room temperature and decrease with increasing Mn concentration. The amorphous Si1−xMnx (x?0.09) semiconductor thin films are p-type and hole densities are 3.73×1018–1.33×1022 cm−3 at room temperature. Low temperature magnetization characteristics reveal that amorphous Si1−xMnx (x?0.09) semiconductor thin films are paramagnetic. 相似文献
16.
Five-layered Si/SixGe1−x films on Si(1 0 0) substrate with single-layer thickness of 30 nm, 10 nm and 5 nm, respectively were prepared by RF helicon magnetron sputtering with dual targets of Si and Ge to investigate the feasibility of an industrial fabrication method on multi-stacked superlattice structure for thin-film thermoelectric applications. The fine periodic structure is confirmed in the samples except for the case of 5 nm in single-layer thickness. Fine crystalline SixGe1−x layer is obtained from 700 °C in substrate temperature, while higher than 700 °C is required for Si good layer. The composition ratio (x) in SixGe1−x is varied depending on the applied power to Si and Ge targets. Typical power ratio to obtain x = 0.83 was 7:3, Hall coefficient, p-type carrier concentration, sheet carrier concentration and mobility measured for the sample composed of five layers of Si (10 nm)/Si0.82Ge0.18 (10 nm) are 2.55 × 106 /°C, 2.56 × 1012 cm−3, 1.28 × 107 cm−2, and 15.8 cm−2/(V s), respectively. 相似文献
17.
BiFeO3/Zn1−xMnxO (x = 0-0.08) bilayered thin films were deposited on the SrRuO3/Pt/TiO2/SiO2/Si(1 0 0) substrates by radio frequency sputtering. A highly (1 1 0) orientation was induced for BiFeO3/Zn1−xMnxO. BiFeO3/Zn1−xMnxO thin films demonstrate diode-like and resistive hysteresis behavior. A remanent polarization in the range of 2Pr ∼ 121.0-130.6 μC/cm2 was measured for BiFeO3/Zn1−xMnxO. BiFeO3/Zn1−xMnxO (x = 0.04) bilayer exhibits a highest Ms value of ∼15.2 emu/cm3, owing to the presence of the magnetic Zn0.96Mn0.04O layer with an enhanced Ms value. 相似文献
18.
The effect of electron-beam irradiation on the magnetic properties of (Ga1−xMnx)As thin films grown on GaAs (100) substrates by using molecular beam epitaxy was investigated. The ferromagnetic transition temperature (Tc) of the annealed (Ga0.933Mn0.067)As thin films was 160 K. The Tc value for the as-grown (Ga0.933Mn0.067)As thin films drastically decreased with increasing electron-beam current. This significant decrease in the Tc value due to electron-beam irradiation originated from the transformation of Mn substituted atoms, which contributed to the ferromagnetism, into Mn interstitials or Mn-related clusters. These results indicate that the magnetic properties of (Ga1−xMnx)As thin films grown on GaAs (100) substrates are significantly affected by electron-beam irradiation. 相似文献
19.
(Ga1−xMnx)N/GaN digital ferromagnetic heterostructures (DFHs) and (Ga1−xMnx)N/GaN grown on GaN buffer layers by using molecular beam epitaxy have been investigated. The photoluminescence (PL) spectra showed band-edge exciton transitions. They also showed peaks corresponding to the neutral donor-bound exciton and the exciton transitions between the conduction band and the Mn acceptor, indicative of the Mn atoms acting as substitution. The magnetization curves as functions of the magnetic field at 5 K indicated that the saturation magnetic moment in the (Ga1−xMnx)N/GaN DFHs decreased with increasing Mn mole fraction and that the saturation magnetic moment and the coercive field in the (Ga1−xMnx)N/GaN DFHs were much larger than those in (Ga1−xMnx)N thin films. These results indicate that the (Ga1−xMnx)N/GaN DFHs hold promise for potential applications in spintronic devices. 相似文献
20.
C.Y. Zhan 《Applied Surface Science》2007,253(18):7478-7482
Ge1−xCx films deposited by using a medium frequency magnetron sputtering technique (MFMST) were analyzed with X-ray photoelectron and Raman spectroscopy. The deposited Ge1−xCx films consist of C, Ge, GeC and GeOy. The GeC content in the Ge1−xCx films linearly decreases, and the C content linearly increases with increasing deposition temperature from 150 to 350 °C. The GeC content decreases from 11.6% at a substrate bias of 250 V to a lowest value of 9.6% at 350 V, then increases again to 10.4% at 450 V. While the C content increases from 49.0% at the bias of 250 V to a largest value of 58.0% at 350 V and then maintains this level at 450 V. It is found that selecting a bias parameter seems more effective than deposition temperature if we want to obtain a higher content of GeC in the deposited films. In addition, a new method is presented in this paper to estimate the changes of GeC content in the Ge1−xCx films by observing the shifts of Ge-Ge LO phonon peak in Raman spectra for the Ge1−xCx films. The related mechanism is also discussed in this paper. 相似文献