【作者】 喻振兴；

【导师】 宋晓岚；

【作者基本信息】 中南大学 ， 材料学， 2010， 硕士

【摘要】 多孔硅因具有独特的发光性能而成为材料界的研究热点。随着对多孔硅材料研究的不断深入,多孔硅制备和性能研究都有了很大进展,但仍然有许多重要问题没有解决,如发光器件发光强度低、发光寿命短、发光稳定性差等。本文采用双槽电化学腐蚀法于光照条件下在n型单晶硅片衬底上制备了n型多孔硅(n-PS),通过室温500～700nm范围内荧光光谱和扫描电镜(SEM)测试系统,研究了光照、腐蚀时间、电解液浓度、腐蚀电流密度及单晶硅掺杂浓度等对n-PS的形成、结构形貌和光致发光(PL)性能的影响。结果表明,通过光照,能获得具有均匀孔分布和良好发光特性的n-PS,在约600nm处产生较强PL峰；随腐蚀时间、HF浓度和电流密度增加,PL峰位先发生蓝移,而后又出现红移；PL发光性能呈先增强后减弱变化趋势,分别在腐蚀时间为20min、HF浓度为6%和电流密度为60mA／cm2时峰强出现极大值；而提高掺杂浓度,PL性能降低。进一步采用脉冲电化学腐蚀制备了n-PS,系统探讨了等效腐蚀时间、脉冲频率、占空比等脉冲电化学腐蚀条件对n-PS室温可见区PL性能的影响。结果表明,该法制备的n-PS比同条件下恒流腐蚀法获得的n-PS的PL强度更高,发光峰位蓝移,且等效腐蚀时间、脉冲频率和占空比均显著影响其PL峰位及发光强度；并用SEM观察其表面形貌,显示形貌更均匀,说明脉冲腐蚀是一种制备n-PS更优良的电化学方法。为了改善多孔硅的发光性能和稳定性,采用电化学沉积Al3+的方法处理用脉冲腐蚀制备的n-PS,以钝化其表面。通过对沉积Al3+前后n-PS的PL光谱、FT-IR光谱(傅里叶变换红外吸收光谱)和SEM图的研究,探讨了Al3+在多孔硅表面的钝化作用及其对PL性能的影响。结果表明,适量沉积Al3+可有效地改善n-PS的光致发光强度和稳定性。其作用机理是Al3+覆盖于多孔硅表面与硅形成稳定的Si-Al键,能够有效地抑制硅悬键的形成,减少非发光中心,从而减缓发光强度的衰减,稳定其发光性能；但过量的Al3+沉积会造成Al3+大量覆盖在n-PS表面导致发光效率降低。更多还原

【Abstract】 Porous silicon has received considerable attention due to its special luminous performance. With deeper research of PS, great progress has been made in the preparation method and performance research, but many vital problems still exist now for its application as luminous apparatus, such as low luminous intensity, short luminous life-span and poor luminous stability.In this study, n-type porous silicon (n-PS) was prepared on monocrystalline silicon wafer by double-cell electrochemical etching method under lighting condition. The effects of light, etching time, HF concentration, current density and dopant concentration of monocrystalline silicon on formation of n-PS, structure, morphology and photoluminescence (PL) performance were studied by scanning electron microscopy (SEM) and PL spectroscopy with wavelength range of 500～700nm. The results showed that the formation, structure, morphology and PL performance of n-PS were controllable, and n-PS with homogenous pore-size distribution and better PL performance under lighting conditions was obtained. A strong PL peak at about 600nm was observed. With increase of etching time, HF concentration and current density, the PL peak showed red shift at first and then blue shift, and the emission intensity increased at first and then decreased. The maximum value of emission intensity was obtained when the corrosion time, HF concentration and current density was 20min,6% and 60mA/cm2, respectively. The PL performance decreased with increase of the monocrystalline silicon dopant concentration.n-PS was also obtained by pulse electrochemical anodization on a phosphorus-doped n-type silicon wafer, which was different from conventional electrochemical anodization method. The effects of equivalent etching time, pulse frequency and pulse duty cycle on PL performance of porous silicon in the visible light range under room temperature were investigated systematically. The results showed that porous silicon obtained by pulse electrochemical etching had higher PL intensity and showed blue shift of luminescent wavelength under the same conditions compared with constant current density anodization. Moreover, the n-PS obtained by pulse electrochemical etching showed a more uniform surface under scanning electron microscope observation, which also proved that pulse electrochemical anodization was a more excellent etching method.In order to improve the PL performance and stability of n-PS, the electrochemical deposition technique was applied to prepare n-PS samples on the surface. The influence of Al-deposited on the photoluminescence of n-PS was studied by PL spectroscopy, Fourier transform infrared spectroscopy and SEM. The results indicated that Al3+ was deposited on PS surface forming stable Al-Si bonds, which could inhibit the formation of dangling Si bonds effectively. Furthermore, the decreased of dangling Si bonds, which were testified to be non-luminescence centers, could retard the attenuation of PL intensity, and stabilized its PL performance. But, on the other hand, excessive Al3+ deposition had a oxidizing effect on room-temperature visible PL of n-PS.更多还原