本文選題：鈦酸鍶鋇 + 脈沖激光沉積��； 參考：《華東師范大學(xué)》2010年碩士論文

【摘要】： 鈦酸鍶鋇(簡稱BST)是一種鐵電／介電性能十分優(yōu)越的材料,因其具有低漏導(dǎo)電流密度、低介質(zhì)損耗、低介電常數(shù)溫度、高介電常數(shù)、熱釋電系數(shù)及其居里點(diǎn)溫度可依據(jù)Ba/Sr比值可調(diào)等特點(diǎn),廣泛應(yīng)用于微波可調(diào)諧器件、動態(tài)隨機(jī)存儲器、熱釋電紅外探測器等方面。隨著科技的發(fā)展,及大規(guī)模集成電路應(yīng)用技術(shù)的發(fā)展和需要,BST鐵電薄膜材料因具備優(yōu)異的電學(xué)和光學(xué)性能,本應(yīng)在應(yīng)用領(lǐng)域中大展身手,卻因?yàn)楸∧ぶ苽浼夹g(shù)上仍然無法達(dá)到領(lǐng)域內(nèi)所期望的高性能指標(biāo)。這一定程度上阻礙了相關(guān)的科技的發(fā)展,因此,BST鐵電材料的性能改善的研究工作有很高的研究價值和需要。 為了解決上述問題,使得鈦酸鍶鋇材料能夠得到更加廣泛的應(yīng)用,本文主要研究了以下內(nèi)容并將研究結(jié)果簡單介紹如下： 1.采用脈沖激光沉積的方法,在不同的襯底上制備了BST薄膜樣品,并通過改善工藝,如退火溫度,襯底選擇等,研究了這些工藝條件對薄膜的質(zhì)量和性能包括物性和電學(xué)性質(zhì)的影響。 2.XRD圖譜表明衍射峰的相對強(qiáng)度隨著沉積溫度的增加而增加,隨著沉積溫度的上升,薄膜的生長質(zhì)量和結(jié)晶狀況得到改善。而在鉑金襯底和鎳酸鑭襯底上制備的薄膜樣品均良好結(jié)晶,呈現(xiàn)出不同的取向。在LNO襯底和Pt襯底上沉積的BST薄膜的晶粒尺寸分別為70nm和50nm。使用與鈦酸鍶鋇材料晶格結(jié)構(gòu)類似的鎳酸鑭薄膜作為襯底,薄膜的晶粒尺寸有明顯的增加。結(jié)果也表明,襯底的選擇的確對薄膜的取向和結(jié)晶性能有很顯著的影響。 3.AFM的測試結(jié)果表明,在LNO和Pt襯底基片上生長的鈦酸鍶鋇薄膜均結(jié)晶良好,表面光滑,無針洞裂紋。在LNO襯底上生長的薄膜樣品,具備更平滑的表面形貌,更大的晶粒尺寸,以及更佳的結(jié)晶狀況。在激光沉積法制備BST薄膜的過程中,BST的微晶成核和動態(tài)生長的過程明顯對襯底的性質(zhì)存在依賴。 4.XPS測試表明采用脈沖激光沉積工藝所制備的BST薄膜中Ba、Sr、Ti、O元素都以鈣鈦礦結(jié)構(gòu)中各元素的相應(yīng)的化學(xué)態(tài)而存在,而AES測試的結(jié)果表明樣品出現(xiàn)了c元素的沾污,這是由于空氣中的碳元素的污染造成的。 5.對所制備樣品進(jìn)行了電學(xué)特性分析,包括CF特性,介電損耗特性,CV特性,PE曲線特性等。分析表明,薄膜樣品的介電特性受到頻率的影響明顯,尤其在高頻區(qū)域。而不同襯底的選擇,會對這一特性有明顯的影響。這和薄膜的微結(jié)構(gòu),以及薄膜和電極間的過渡層的出現(xiàn)有關(guān)。 6.本文中著重研究了BST薄膜的介電特性的不對稱性。結(jié)果表明,介電特性的不對稱性是薄膜本身的性質(zhì)造成,而非加諸的電壓導(dǎo)致。而上下電極的不對稱性,會加重其不對稱性,為改善這一點(diǎn),BST薄膜的上下電極均采用鉑金電極后,顯著改善了不對稱性(薄膜的介電不對稱率由50.38%減小至17.86%)。 7.BST薄膜材料在微波器件的研制領(lǐng)域有著廣闊的前景。在本文的電學(xué)測試中,也著重研究了其介電可調(diào)諧性。結(jié)果表明,薄膜樣品的可調(diào)諧度隨著頻率的上升而一定程度上出現(xiàn)下降趨勢。且可調(diào)諧度受到底電極的影響較為明顯。在LNO底電極上沉積的薄膜表現(xiàn)出更優(yōu)良的可調(diào)諧度,在10kHz和100kHz下分別達(dá)到45.3％和39.5%,而沉積在Pt底電極上的薄膜的可調(diào)諧度均在30%左右,且隨頻率變化不大。薄膜樣品的可調(diào)諧度隨頻率的變化與之前薄膜樣品的C-F特性曲線相吻合。薄膜的微結(jié)構(gòu)和介電性能,直接影響了其可調(diào)諧性能。要制備出可調(diào)諧性良好的薄膜材料,需要對薄膜的生長工藝和薄膜結(jié)構(gòu)進(jìn)行改進(jìn)。 8.對于鈦酸鍶鋇薄膜的鐵電性也進(jìn)行了測試和研究。在8V的測試電壓下,電場強(qiáng)度約為400kv／cm,此時LNO上的樣品的剩余極化強(qiáng)度Pr和矯頑電場Ec分別是0.409μC／cm2和22.04 kV／cm,而Pt上沉積的樣品的對應(yīng)的Pr和Ec分別為0.393μC／cm2和12.09 kV／cm。在Pt緩沖層上沉積的薄膜顯示了更大和更明顯的電滯回線,而在LNO緩沖層上沉積的薄膜的電滯回線沿著電場v=0軸線有一定程度的偏移,這一結(jié)果與CV測試結(jié)果相吻合這可能是由于薄膜的微疇結(jié)構(gòu)上的差異造成的。結(jié)果表明,晶粒的大小和底電極的選擇,對鐵電性有明顯的影響。
[Abstract]:Barium strontium titanate (BST) is an excellent ferroelectric / dielectric material. Because of its low leakage current density, low dielectric loss, low dielectric constant temperature, high permittivity, thermoluminescence coefficient and Curie point temperature can be adjusted according to the Ba/Sr ratio, it should be widely used in microwave tunable devices, dynamic random memory and heat. With the development of science and technology and the development of the application technology of large scale integrated circuits, the BST ferroelectric thin film materials have excellent electrical and optical properties. They should be in the field of application, but because the film preparation technology still fails to reach the expected high performance indicators in the field. To a certain extent, it hinders the development of related technology. Therefore, the research on the performance improvement of BST ferroelectric materials has high research value and needs.
In order to solve the above problems, barium strontium titanate materials can be more widely used. The following contents are mainly studied and the results are briefly introduced as follows:
1. the samples of BST films were prepared on different substrates by pulsed laser deposition, and the effects of these conditions on the quality and properties of the films, including physical properties and electrical properties, were investigated by improving the process, such as annealing temperature and substrate selection.
The 2.XRD map shows that the relative intensity of the diffraction peak increases with the increase of the deposition temperature. With the increase of the deposition temperature, the growth quality and crystallization of the film are improved. The films prepared on the platinum substrate and the lanthanum acid substrate are well crystallized, showing different orientation. The BST thin deposited on the LNO substrate and the Pt substrate. The grain size of the film is 70nm and 50nm., which is similar to the lattice structure of barium strontium titanate as the substrate, and the grain size of the film is obviously increased. The results also show that the selection of the substrate has a significant effect on the orientation and crystallization properties of the films.
The test results of 3.AFM show that barium strontium titanate thin films on the substrate of LNO and Pt have good crystallization, smooth surface and no needle hole cracks. The thin film samples on the LNO substrate have more smooth surface morphology, larger grain size, and better crystallization condition. In the process of preparing BST thin films by laser deposition, BST micro The process of nucleation and dynamic growth obviously depends on the properties of the substrate.
The 4.XPS test showed that the Ba, Sr, Ti and O elements in the BST films prepared by pulsed laser deposition were all in the chemical state of the elements in the perovskite structure, and the results of AES test showed that the samples were contaminated by the C elements, which was caused by the pollution of the carbon elements in the air.
5. the electrical characteristics of the prepared samples were analyzed, including CF characteristics, dielectric loss characteristics, CV characteristics, and PE curve characteristics. The analysis showed that the dielectric properties of the films were affected by frequency, especially at high frequency regions. The selection of different substrates would have a significant effect on this specificity. This and the microstructure of the film, and film It is related to the appearance of the transition layer between the electrodes.
6. in this paper, the asymmetry of dielectric properties of BST films is emphatically studied. The results show that the asymmetry of dielectric properties is caused by the properties of the film itself, not the voltage added, and the asymmetry of the upper and lower electrodes will aggravate its asymmetry. In order to improve this point, the upper and lower electrodes of the BST film are changed to a platinum electrode. The asymmetry of the dielectric asymmetry is reduced from 50.38% to 17.86%.
7.BST thin film materials have a broad prospect in the development of microwave devices. In the electrical test, the dielectric tunability is also studied. The results show that the tunability of the thin film samples decreases with the increase of frequency. And the tunability is influenced by the electrode. At the bottom of the LNO, the tunability is more obvious. The deposited film shows a better tunability at 45.3% and 39.5% under 10kHz and 100kHz respectively, while the tunability of the films deposited on the Pt substrate is about 30%, and the frequency varies little with the frequency. The tunability of the film samples coincides with the C-F characteristic curve of the thin film samples. The microstructure and dielectric properties directly affect its tunable properties. To prepare thin film materials with good tunability, it is necessary to improve the film growth process and thin film structure.
8. the ferroelectric properties of barium strontium titanate thin film are also tested and studied. Under the test voltage of 8V, the electric field strength is about 400kV / cm. At this time, the residual polarization strength of the samples on LNO and the coercive electric field Ec are 0.409 C / cm2 and 22.04 kV / cm respectively, while the corresponding Pr and 12.09 samples are 0.393 Mu and 12.09 respectively. The film deposited on the Pt buffer layer of cm. shows a larger and more obvious hysteresis loop, and the hysteresis loop of the film deposited on the LNO buffer layer is offset to a certain extent along the v=0 axis of the electric field. This result is in agreement with the CV test results, which may be due to the difference on the microdomain structure of the film. The result shows that the grain size is large. The choice of small and bottom electrodes has a significant effect on ferroelectricity.
【學(xué)位授予單位】：華東師范大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2010
【分類號】：TM221

【參考文獻(xiàn)】

相關(guān)期刊論文 前3條

1 敖育紅,胡少六,龍華,徐業(yè)斌,王又青;脈沖激光沉積薄膜技術(shù)研究新進(jìn)展[J];激光技術(shù);2003年05期

2 肖定全;集成鐵電學(xué)與鐵電集成薄膜[J];物理;1994年10期

3 劉梅冬,陳實(shí),李元昕,曾亦可,姜勝林,鄧傳益,劉少波;鐵電薄膜熱釋電非致冷紅外傳感器研究[J];儀表技術(shù)與傳感器;2004年02期

，

本文編號：2024471