【摘要】：SrTiO_3是一種典型的,具有鈣鈦礦結(jié)構(gòu)的,寬禁帶金屬氧化物,其本征禁帶寬度大約在3.2eV。室溫下,本征SrTiO_3不導(dǎo)電,屬于絕緣體,但是通過適量的摻雜改性,可以變?yōu)榘雽?dǎo)體甚至超導(dǎo)體。通過改性的SrTiO_3在特定波長光的照射下會發(fā)光,而且在光照的條件下可以分解水制氫,分解有機污染物,也可以用作固體氧化物燃料電池,是一種很有潛力的光電材料。主要研究內(nèi)容及結(jié)果:一、本文主要對p型SrTiO_3進行研究,首先對p型SrTiO_3進行理論研究,理論研究是基于第一性原理的計算,我們在Materials Studio 6.1軟件中用CASTEP軟件包進行計算,根據(jù)所查閱資料,我們確定了研究體系,以第Ⅲ主族元素摻雜為主,因此,我們計算了第Ⅲ主族常用元素(Al,Ga,In)的摻雜體系,主要計算了Al、Ga、In在同一摻雜濃度下的晶胞常數(shù),形成焓,能帶結(jié)構(gòu),電荷性質(zhì),電子態(tài)密度以及光學(xué)性質(zhì),從微觀上揭示了摻雜元素對SrTiO_3電子結(jié)構(gòu)和光學(xué)性質(zhì)影響的機理。計算結(jié)果顯示,Al、Ga、In摻雜SrTiO_3為p型摻雜,與本征SrTiO_3相比,摻雜后在可見光處均出現(xiàn)了吸收,這對于研究SrTiO_3的光催化性能,提供了新的方向。二、通過第一部分的研究我們得到,第Ⅲ主族元素摻雜SrTiO_3可以實現(xiàn)p型摻雜,我們對不同濃度Al摻雜SrTiO_3進行了計算,分別為1.11at%,2.22at%,3.33at%。計算的內(nèi)容包括晶體結(jié)構(gòu),形成焓,能帶結(jié)構(gòu),總態(tài)密度及分態(tài)密度以及光學(xué)性質(zhì)。計算結(jié)果顯示了,在一定濃度范圍內(nèi),隨著Al摻雜的濃度升高,摻雜體系的穩(wěn)定性逐漸下降,體系的帶隙逐漸增加,對可見光的吸收逐漸下降,計算結(jié)果表明,Al摻雜SrTiO_3濃度在1.11at%時,穩(wěn)定性良好,光學(xué)吸收強,可為實驗提供數(shù)據(jù)參考理論依據(jù)。三、運用射頻磁控濺射,在室溫下制備了本征和不同濃度Al摻雜SrTiO_3薄膜。根據(jù)前面的計算,我們制備了1.1%,2.2%,3.3%三種摻雜濃度的薄膜,并進行了退火處理。測量了薄膜的透過率,吸收值,以及光致發(fā)光光強度,分析數(shù)據(jù),我們得到,Al摻雜SrTiO_3薄膜在可見光區(qū)中,它的透過率減小了,在可見光區(qū)中,它的吸收增強了。在一定濃度范圍內(nèi),隨著摻雜的Al濃度的增加,光學(xué)帶隙先減小后增大。我們還發(fā)現(xiàn)雜質(zhì)元素,對發(fā)光峰位置基本沒有影響,只是增大了發(fā)光強度。四、通過第一性原理計算方法,我們計算了N摻雜SrTiO_3,N-Al共摻雜SrTiO_3的電子結(jié)構(gòu),能帶結(jié)構(gòu),形成焓,態(tài)密度和光學(xué)性質(zhì),我們經(jīng)過分析得到,N摻雜SrTiO_3表現(xiàn)為P型摻雜,帶隙減小了。與N摻雜相比,N-Al共摻雜SrTiO_3空穴濃度有所增加,并且在可見光區(qū)域出現(xiàn)了較強吸收。表現(xiàn)出更加優(yōu)異的性能。
[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.
【學(xué)位授予單位】：魯東大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O469

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