The growth of environmental semiconductor β-FeSi_2 films for light emitting devices and photo-detection devices

正交晶系β-FeSi_2由地球上大量存在的无毒元素组成。β-FeSi_2在热电器件、发光器件和光伏电池等方面具有广阔的应用前景。本研究利用脉冲激光沉积法（PLD）在Si衬底上生长β-FeSi_2薄膜，并对其光学性质进行了研究。（1）β-FeSi_2薄膜不是在室温下生长的，衬底温度超过400 ℃时，β-FeSi_2为单晶结构。（2）在Si（111）衬底上制备的样品，由于只观察到β-FeSi_2的（202）或（220）信号，所以是单晶结构。（3）制备的β-FeSi_2的组成为Fe：Si=30：70。沉积态β-FeSi_2是富硅的。（4）室温和500 ℃时，铁扩散到Si衬底中，扩散量大。(5)400 ℃制备的β-FeSi_2/Si界面是理想的单边台阶结。（6）当退火时间超过20小时时，β-FeSi_2薄膜的半高宽下降了50%左右，并且出现了晶化恢复现象。β-FeSi_2组分比接近化学计量比。带隙增大。（7）铁和晶格缺陷成为杂质能级，被认为是发光的杀伤中心。(8)We发现Si衬底上的β-FeSi_2薄膜在900℃退火40 h后的PL峰位于0.807eV处。首次用PLD技术观察到β-FeSi_2薄膜的光致发光信号。沉积态样品的PL峰被认为是Si缺陷峰，并出现了Si络合物峰。

Orthorhombic the β-FeSi_2 is composed of nontoxic elements, which exist in great abundance on earth. The use of the β-FeSi_2 is expected in applications of thermoelectric devices, light emitting devices and photovoltaic cells. In this study, we attempted to grow the β-FeSi_2 thin film on Si substrate, using a pulsed laser deposition method (PLD), for investigating optical properties.(1)The β-FeSi_2 thin films were not grown at room temperature and substrate temperature over 400 degrees made the β-FeSi_2 monocrystalline structure.(2)The sample prepared on Si(111) substrate was a monocrystalline structure since only (202) or (220) signals of β-FeSi_2 were observed.(3)Composition of produced β-FeSi_2 was Fe:Si=30:70. So as-deposition β-FeSi_2 was Si-rich.(4)Iron was spread into Si substrate and the amount of diffusion was large at room temperature and 500 degrees.(5)β-FeSi_2/Si interface prepared by 400 degrees was an ideal one-side step junction.(6)When we used the annealing above 20 hours, the FWHM of β-FeSi_2 thin film was decreased about 50% and the crystalline recovery was observed. And β-FeSi_2 composition ratio was close to stoichiometry. And the band gap was increased.(7)Iron and a lattice defect were made impurity level and were considered to operate as a killer center of luminescence.(8)We found that the PL peaks from the β-FeSi_2 thin films on a Si substrate appear at 0.807eV for the samples annealed at 900℃ for 40h. The PL signal from the β-FeSi_2 thin film was observed using PLD for the first time to the best of our knowledge. And the PL peak of as-deposited sample is considered that Si defective peak ; and Si complex peak appeared.