| The aluminum nitride is a III-nitride semiconductor material with the most wideband gap width (6.2eV), the emission wavelength with the band can be into the deepultraviolet band,which can lead to potential applications in the emerging field ofultraviolet and deep ultraviolet electronics. AIN can be used as the substrate materialsfor other luminous body due to the width of band gap, has a widespread use in thefield of advanced ceramics, composite materials, electronic materials. AIN has verybroad potential application in aspects as communication technology, so is the mainraw material for the development of short wavelength optoelectronic devices and hightemperature, microwave electronic devices.GaN is wide bandgap semiconductor, the direct band gap of3.4eV at roomtemperature, has a potential application in the field of blue light electronicsapplications. GaN is a good material with luminescence performance due to its goodthermal performance, small dielectric coefficient, high in saturated electron driftvelocity, which is an ideal material for light emitting device. It plays a key role inapplication in the preparation of high power and high temperature integrated circuits.And it has very important potential application in the preparation of photoelectron,CCD and high speed microwave communication devices used in extreme conditions.The aluminum nitride and gallium nitride is important semiconductor in the thirdgeneration of semiconductor materials. At present, III-nitride based diluted magneticsemiconductors (DMSs) have been predicted with high Curie temperature, so thesynthesis of III-nitride based DMSs and the study of property is a frontier and hotissue in today’s international nano materials research field. When the cation portion ofsemiconductor is replaced partly and disorderly by some doping metal ions, making ithave the properties of semiconductor and ferromagnetic at same time, is considered tobe of great application prospect in the new functional materials. Thus, the researchand exploration for this type of dilute magnetic semiconductor doping characteristic and the performance, and discussing the origin of magnetism and testifying the resultof theory can open up a new path for development and production of new functionalnano DMSs devices.The nanomaterials has different properties with bulk materials, a great deal ofattention has been devoted to the research of nanomaterial and the change of physicalproperties under the high pressure. A larger number of literature investigationsindicate that there is a small amount of reports about the exploration of high pressuretechnology in nanomaterial under extreme conditions, and there is a few studies aboutthe property of III-nitride based DMSs under high pressure.Based on the above understanding, the different morphology Mg, Co dopedaluminum nitride dilute magnetic semiconductors have been synthetized by the dc arcplasma method, and studied and analysed the structure, morphology, and property. Inaddition, we study the high pressure physical properties of the Co doped AlNnanowires with the diameter of70nm using in situ synchrotron radiation X-raydiffraction technique in diamond anvil cell.The main results are as follows:1. The AlN: Co nanomaterials with different morphology were synthesized, suchas nanowires, comb structure, dendritical structure; Al (purity99.99%)，Co (purity99.99%)，and N2(purity99.99%) were used as sources. Phase,structural and chemicalcomposition analyses of the AlN: Co were carried out using X-ray diffraction (XRD),scanning electron microscopy(SEM), transmission electron microcopy (TEM), andenergy dispersive spectroscopy (EDS). The size of samples are relate to the inputcurrent and the reaction time. The small size of sample is produced under the smallinput current and short reaction time, conversely to increase. The magnetic propertywas carried out using vibrating sample magnetometer (VSM), it proves that thesesamples are ferromagnetic at room temperature.An arc discharge plasma setup is improved by adding a Mo on cathode tungstenpole piece. It is succeed in the six heavy structure of AlN: Co on the basal AlCo blockand on the Mo slice. Phase,structural and chemical composition analyses of thisstructure has been studied. There is a small area of the airflow circulation space in the reaction chamber, we can get the different morphology sample at the same time. Themagnetic property was carried out using vibrating sample magnetometer (VSM), itproves that these samples are ferromagnetic at room temperature. The intensity ofmagnetism is larger than pure AlN: Co nanostructure due to the presence of Coimpurity.2. The AlN: Mg nanomaterials with different morphology were synthesized, suchas nanowires, dendritical structure, etc.; Al (purity99.99%)，Mg (purity99.99%)，andN2(purity99.99%) were used as sources. Phase,structural and chemical compositionanalyses of the AlN: Mg were carried out using X-ray diffraction (XRD), scanningelectron microscopy(SEM), transmission electron microcopy (TEM), and energydispersive spectroscopy (EDS). The size of samples are relate to the input current andthe reaction time. The small size of sample is produced under the small input currentand short reaction time, conversely to increase. The magnetic property was carried outusing vibrating sample magnetometer (VSM), it proves that these samples areferromagnetic at room temperature.3. The GaN:Mn nanomaterials with different morphology were synthesized, suchas nanowires, comb structure, dendritical structure; Mn (purity99.99%)，GaO (purity99.99%)，and the mixture of N2and NH3(purity99.99%) were used as sources.Phase,structural and chemical composition analyses of the GaN:Mn were carried outusing X-ray diffraction (XRD), scanning electron microscopy(SEM). The size ofsamples are relate to the input current and the reaction time. The small size of sampleis produced under the small input current and short reaction time, conversely toincrease. The magnetic property was carried out using vibrating sample magnetometer(VSM), it proves that these samples are ferromagnetic at room temperature.4. High-pressure behaviors of AlN:Mg and AlN:Co nanowires have beeninvestigated by in situ angle dispersive synchrotron X-ray diffraction up to41.5and38.2GPa, respectively. Their corresponding pressure-induced wurtzite-to-rocksaltphase transitions start at17.7and15.0GPa and complete at33.2and31.0GPa,respectively. The phase-transition routes are not affected by the doped ions, while the phase transition pressures are lower than those of pure AlN nanowires. The distincthigh-pressure behaviors are ascribed to the doped ions, which reduce the formationenergy of cation vacancies and induce Al vacancy defects together with substitutiondefects, resulting in lattice distortion, and affecting structural stability and phasetransition pressure. The doping causes the reduction of phase transition pressure andphase transition barriers, and accelerates the phase transition. The bulk modulus ofwurtzite phases were determined to be B0=252.6±6.6GPa and B0=245.0±7.8GPa forAlN:Mg and AlN:Co nanowires, respectively. The phase transition pressure and bulkmodulus of the doped nanowires decreases in contrast to pure AlN nanowires, and thedecrease degree of the doped Co nanowires is larger than that of the doped Mg.Because Co2+(rCo=0.745)>Mg2+(rMg=0.72), doped Co ions give rise to largerinfluence on the stability of lattice structure and cause the larger lattice distortion thanthat of doped Mg ions, resulting in the phase transition pressure of AlN:Co nanowiresbeing lower than that of AlN: Mg nanowires. Under high pressure, stress focuses ondefects of crystal; larger local stress impels the beginning of phase transition andreduces the phase transition pressure. Mg or Co ions residing at the Al ions sites mightreduce the phase transition barriers; fill a post with preferred nucleation sites andaccelerate the completion of the phase transition. Our experimental results prove thatchange the stability of the samples and phase transition pressure, leading to a moretheoretical and experimental work. |
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