P型钛酸锶材料电子结构及其光电性能的研究

发布时间：2019-06-05 16:35

【摘要】：SrTiO_3是一种典型的,具有钙钛矿结构的,宽禁带金属氧化物,其本征禁带宽度大约在3.2eV。室温下,本征SrTiO_3不导电,属于绝缘体,但是通过适量的掺杂改性,可以变为半导体甚至超导体。通过改性的SrTiO_3在特定波长光的照射下会发光,而且在光照的条件下可以分解水制氢,分解有机污染物,也可以用作固体氧化物燃料电池,是一种很有潜力的光电材料。主要研究内容及结果:一、本文主要对p型SrTiO_3进行研究,首先对p型SrTiO_3进行理论研究,理论研究是基于第一性原理的计算,我们在Materials Studio 6.1软件中用CASTEP软件包进行计算,根据所查阅资料,我们确定了研究体系,以第Ⅲ主族元素掺杂为主,因此,我们计算了第Ⅲ主族常用元素(Al,Ga,In)的掺杂体系,主要计算了Al、Ga、In在同一掺杂浓度下的晶胞常数,形成焓,能带结构,电荷性质,电子态密度以及光学性质,从微观上揭示了掺杂元素对SrTiO_3电子结构和光学性质影响的机理。计算结果显示,Al、Ga、In掺杂SrTiO_3为p型掺杂,与本征SrTiO_3相比,掺杂后在可见光处均出现了吸收,这对于研究SrTiO_3的光催化性能,提供了新的方向。二、通过第一部分的研究我们得到,第Ⅲ主族元素掺杂SrTiO_3可以实现p型掺杂,我们对不同浓度Al掺杂SrTiO_3进行了计算,分别为1.11at%,2.22at%,3.33at%。计算的内容包括晶体结构,形成焓,能带结构,总态密度及分态密度以及光学性质。计算结果显示了,在一定浓度范围内,随着Al掺杂的浓度升高,掺杂体系的稳定性逐渐下降,体系的带隙逐渐增加,对可见光的吸收逐渐下降,计算结果表明,Al掺杂SrTiO_3浓度在1.11at%时,稳定性良好,光学吸收强,可为实验提供数据参考理论依据。三、运用射频磁控溅射,在室温下制备了本征和不同浓度Al掺杂SrTiO_3薄膜。根据前面的计算,我们制备了1.1%,2.2%,3.3%三种掺杂浓度的薄膜,并进行了退火处理。测量了薄膜的透过率,吸收值,以及光致发光光强度,分析数据,我们得到,Al掺杂SrTiO_3薄膜在可见光区中,它的透过率减小了,在可见光区中,它的吸收增强了。在一定浓度范围内,随着掺杂的Al浓度的增加,光学带隙先减小后增大。我们还发现杂质元素,对发光峰位置基本没有影响,只是增大了发光强度。四、通过第一性原理计算方法,我们计算了N掺杂SrTiO_3,N-Al共掺杂SrTiO_3的电子结构,能带结构,形成焓,态密度和光学性质,我们经过分析得到,N掺杂SrTiO_3表现为P型掺杂,带隙减小了。与N掺杂相比,N-Al共掺杂SrTiO_3空穴浓度有所增加,并且在可见光区域出现了较强吸收。表现出更加优异的性能。
[Abstract]:SrTiO_3 is a typical perovskite structure, wide band gap metal oxide, its intrinsic band gap width is about 3.2 EV. At room temperature, intrinsic SrTiO_3 is not conductive and belongs to insulator, but it can be changed into semiconductor or even superconductor by proper doping modification. The modified SrTiO_3 can emit light under the irradiation of specific wavelength light, and it can decompose water to hydrogen and organic pollutants under the condition of light, and it can also be used as solid oxide fuel cell. It is a potential optoelectronic material. The main research contents and results are as follows: first, this paper mainly studies p-type SrTiO_3, first of all, the theoretical research of p-type SrTiO_3 is based on the first-principle calculation. We use CASTEP software package to calculate in Materials Studio 6.1. according to the data consulted, we determine the research system, which is mainly adulterated with the third main group element. therefore, we calculate the common elements of the third main group (Al,Ga,). The crystal cell constant, formation enthalpy, band structure, charge property, electronic state density and optical properties of Al,Ga,In at the same doping concentration were calculated. The mechanism of the effect of doping elements on the electronic structure and optical properties of SrTiO_3 is revealed from the microscopic point of view. The calculated results show that Al,Ga,In doped SrTiO_3 is p-type doping, compared with intrinsic SrTiO_3, the absorption occurs at visible light after doping, which provides a new direction for the study of photocatalytic performance of SrTiO_3. Secondly, through the first part of the study, we get that the p-type doping can be realized by doping SrTiO_3 with the third main group element. we have calculated the SrTiO_3 doping with different concentrations of Al, which are 1.11at%, 2.22at% and 3.33at%, respectively. The calculated contents include crystal structure, enthalpy of formation, band structure, total density of states, partial density of states and optical properties. The calculated results show that in a certain concentration range, with the increase of Al doping concentration, the stability of the doping system decreases gradually, the band gap of the system increases gradually, and the absorption of visible light decreases gradually. When the concentration of Al doping SrTiO_3 is 1.11at%, the stability is good and the optical absorption is strong, which can provide a theoretical basis for the experiment. 3. Intrinsic and different concentrations of Al-doped SrTiO_3 thin films were prepared by RF magnetron sputtering at room temperature. According to the previous calculations, we prepared 1.1%, 2.2% and 3.3% of the films with three doping concentrations and annealed them. The transmittance, absorption value and photoluminescence intensity of the films were measured. The results show that the transmittance of Al-doped SrTiO_3 thin films decreases in the visible region, and its absorption is enhanced in the visible region. In a certain concentration range, with the increase of doping Al concentration, the optical band gap decreases at first and then increases. We also find that impurity elements have little effect on the position of luminous peak, but increase the luminous intensity. 4. By means of the first principle calculation method, we have calculated the electronic structure, band structure, enthalpy of formation, density of states and optical properties of N-doped SrTiO_3,N-Al co-doping SrTiO_3. N-doped SrTiO_3 showed P-type doping and the band gap decreased. Compared with N doping, the hole concentration of N-Al co-doping SrTiO_3 is increased, and the absorption is strong in the visible region. Show better performance.
【学位授予单位】：鲁东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O469

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