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Structure and Properties of AlN and Fe-doped AlN Films

Author: GaoXuDong
Tutor: JiangEnYong
School: Tianjin University
Course: Materials Physics and Chemistry
Keywords: AlN films Optical band gap Index of refraction Fe-doped AlN thin films Diluted magnetic semiconductor
CLC: TB383.2
Type: Master's thesis
Year: 2007
Downloads: 172
Quote: 1
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Abstract


Aluminum nitride (AlN) film having a wide band gap, the higher the velocity of the surface acoustic wave, excellent piezoelectric properties, high thermal stability and corrosion resistance, emitting in the UV, light detecting acoustic surface wave devices has broad application prospects. The theory predicts that the AlN films doped with transition metal element is ferromagnetic at room temperature, application in spintronics devices and quantum computers. This thesis by DC magnetron sputtering, undoped and Fe-doped AlN thin films were prepared by N 2 partial pressure and total sputtering gas pressure (Ar N 2 < / sub>) the size of the structure and optical properties of AlN films were systematically studied, and Fe-doped AlN thin film structure and magnetic properties were studied. Study by preparative state AlN film, found N 2 stars pressure changes can affect the energy and the mobility of the particles are deposited so that the thin-film crystal orientation and the surface roughness is changed, and at the same time cause the film defect concentration changes, which makes the compound state of the thin film elements and thin film optical properties change. By using the Hermite interpolation method, there is obtained a spectral transmittance curve of the package, and using Swanepoel method to calculate the refractive index of the film, when the incident light wavelength of 550 nm, the refractive index of the obtained film in between 1.84-1.91, With the N 2 partial pressure increases monotonically increasing; when the wavelength of the incident light near 200 nm, the film strongly absorbed incident light, and the defect concentration decreases, resulting in the absorption edge with with N 2 partial pressure increases the blue shift of the optical band gap increases from 5.83 eV to 5.91 eV. In 10% N 2 partial pressure of the films of the transmission spectrum, 4.03 eV and 5.83 eV found two strong absorption. The study found that, due to the weakening of collision caused by the loss of energy of the sputtered particles, the lower the total sputtering gas pressure is conducive to the formation of the higher energy of the crystal plane. However, due to the lower total sputtering gas pressure will result in the decrease of the film density and the N content, therefore the refractive index of the film and the optical band gap values ??corresponding smaller. Obtained by calculation, when the total sputtering gas pressure increased from 1.5 Pa to 2.5 Pa, a wavelength of the light wave of 550 nm, the refractive index between 1.86-1.90, its optical band gap of 5.87 eV-5.89 eV of The rooms are increased with the increase in the total sputtering gas pressure. Use of a sputtering method incorporated in the type of the content of Fe element in the AlN film. The study found that when the lower amount of Fe doping elements, Fe atoms in the crystal lattice in the main occupy alternate location; but with the increase in the amount of the Fe-doped, Fe atoms occupy the interstitial position, while Fe-N compound state and miscellaneous metal Fe phase. At room temperature, all of the doped film are ferromagnetic phenomenon, its saturation magnetization decreases with the increase in the amount of Fe doping. When the Fe doping content of 1.2%, a saturation magnetization of the film is 2.81 emu / cm 3 , equivalent effective average atomic magnetic moments about 0.3μB/Fe. The analysis showed that the ferromagnetism of the film comes from the AlFeN ternary alloy. Through change N 2 sub-pressure size, research N 2 partial pressure of the structure, surface morphology and optical properties of Fe-doped AlN films. The results showed that the N 2 stars pressure increase can be promoted in a certain extent of Fe atoms into the lattice, the crystal surface is increased formation energy, thus promoting the formation energy is lower (102) crystal plane The formation of the the larger N 2 stars pressure can promote the formation of the (002) crystal plane formed higher by increasing the energy of the particles are deposited. With N 2 stars pressure increases, the surface of the particles of the film thinning occurs, more densely arranged, particles undulating reduced, surface roughness decreased rapidly. Studies show that for the transmission spectra of the films as the the N 2 stars pressure increases, the transmittance of the film is relatively increased, and the absorption edge of the blue shift.

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