介质环境对KDP晶体微观形貌及生长速率的影响研究

发布时间：2018-08-03 12:21

【摘要】：随着惯性约束核聚变(Inertial Confinement Fusion,ICF)工程的发展,人们对KDP晶体的需求、质量、生长速度等都提出了更高的要求,可以概括为"快速、大尺寸、高质量"。"快速":可以提供工程上所需要的KDP晶片数量,缩短生长周期,降低成本。"大尺寸":可以满足ICF系统装置中对晶体尺寸的要求。"高质量":可以达到ICF装置对KDP晶体性能要求的指标,如高的激光损伤阈值、高的透过率、高的光学均匀性等。近年来,人们对KDP晶体的研究主要在生长工艺、光学质量、晶体结构等方面。我们认为要从根本上提高KDP晶体的生长速度、光学性能,应该对晶体生长的微观形貌以及生长机制进行研究。作为经典的水溶液生长晶体,温度、过饱和度、杂质、pH等介质环境对KDP晶体的生长习性、光学质量等都有着重要的影响。因此,本文主要选择通过改变生长溶液的饱和温度、过饱和度、pH值,以及通过掺杂金属离子杂质、有机添加剂的方式,来研究各种介质因素对KDP晶体生长台阶的微观形貌、生长速度的影响,对不同条件下生长所得的晶体进行激光损伤阈值的测试,并对其影响机理进行了初步的探讨研究。本论文的主要内容如下:1.在不同饱和温度的溶液,不同的过饱和度下生长了 KDP晶体,测试了晶体的激光损伤阈值。利用原子力显微镜观察了不同条件下KDP晶体的表面微观形貌。通过激光偏振干涉系统实时测量了在不同温度下,KDP晶体的生长速度与过饱和度之间的关系。实验结果表明:在低温度区域(~35℃C)下,晶体表面生长台阶在低过饱和度(σ=0.01)、中间过饱和度(σ=0.05)以及高过饱和度(σ=0.08)下,都出现了聚并升高的现象,宏台阶包含基本台阶的个数分别平均为21、22、59个。与此相对应的,台阶的斜率也在这三个过饱和度下出现了峰值,分别为9.26×10-3、9.64×10-3、8.47×10-3。另外,在高过饱和度σ=0.08时,晶体表面出现"树枝状"台阶,我们认为可能与台阶上存在着Ehrlich-Schwoebel(E-S)势垒有关。在中温度区域(~45℃C、55℃C)下,晶体表面的台阶聚并程度都在σ=0.04时出现峰值,此时,在45℃C下生长的台阶的高度要略高于55℃C的情况。在晶体生长过程中,台阶的斜率都在中间过饱和度区域出现一个峰值,45℃C时,斜率的峰值出现在σ=0.06时,而55℃C时峰值对应的过饱和度要低,在σ=0.04时。这两个峰值位置所对应的台阶宽度都是急剧降低的。在高过饱和度下,台阶的聚并程度和台阶斜率都随过饱和度的升高而增大,其中55℃C时更为显著。在高温度区域(~65℃C)下,晶体表面生长台阶的聚并程度和台阶斜率都随着过饱和度的升高呈现出先增大后减小的趋势,都在过饱和度σ=0.03时出现峰值,此时宏台阶包含基本台阶的个数大约为48个,台阶的斜率约为8.8×10-3。在高过饱和度σ=0.08和σ=0.09时,晶体表面出现"凹坑"或者"孔洞",这些"孔洞"被台阶上的突起所包围,我们认为这些突起是由二维成核机制产生的,这也说明此时台阶的生长是位错台阶的推移和二维成核生长机制共同作用的结果。KDP晶体在不同饱和温度的溶液中,台阶的推移速度都随着过饱和度的增加呈现出相似的规律,晶体生长过程中的过饱和度死区σd、线性过饱和度σ*、延长线通过原点的临界过饱和度σ'将v(σ)曲线大致分为三个区域,这三个过饱和度都随着温度的升高而减小。另外,在相同的过饱和度下,台阶推移速度随着温度的升高而增大。在不同饱和温度下生长的KDP晶体的激光损伤阈值都随着过饱和度的增加呈现出先减低后升高的趋势,类似于"V"形变化。2.通过掺杂的方式,研究Fe~(3+)杂质在不同的温度、过饱和度下对KDP晶体生长习性的影响。利用原子力显微镜技术和激光偏振干涉技术分别研究不同条件下KDP晶体(100)表面生长台阶的微观形貌和生长速度。实验结果表明:利用传统降温法生长的KDP晶体,随着溶液中Fe~(3+)掺杂浓度的升高,台阶的聚并程度和斜率都增大,台阶分布的均匀性下降,生长死区变大,生长速度降低。当Fe~(3+)浓度为30ppm时,在不同饱和温度的溶液中,KDP晶体的生长速度随着温度的升高而增大。在高温区域(~65℃C、75℃C),KDP晶体在掺杂溶液中的生长速度要快于在未掺杂的溶液中。在饱和温度约为55℃C,溶液中的Fe~(3+)浓度为5ppm时,KDP晶体的台阶的聚并程度只有在低过饱和度(σ=0.02)时高于未掺杂的情况。此时台阶非常直,生长均匀,并且在宽的台阶阵列上明显分布着许多基本台阶。当Fe~(3+)浓度为30ppm时,台阶的聚并程度随过饱和度的升高而增大,在相同的过饱和度下都大于未掺杂时的情况。当Fe~(3+)浓度为50ppm时,在低过饱和度下,台阶的聚并非常高;在高的过饱和度下,台阶扭折增多,变大。3.在溶液中加入100ppm、500ppm的有机添加剂CDTA,采用点籽晶快速法生长了 KDP晶体。利用原子力显微镜技术从原子层面观察不同浓度的CDTA对KDP晶体表面生长台阶微观形貌的影响,通过激光偏振干涉技术测量KDP晶体在掺杂不同浓度CDTA溶液中的台阶推移速度。实验结果表明:CDTA并没有进入KDP晶体内部,CDTA对晶体生长的作用主要发生在溶液中的生长基元向晶体扩散的过程中。有机添加剂CDTA对KDP晶体生长习性的影响可以分为积极和消极两个方面。当溶液中添加适量浓度的CDTA时,其能够与溶液中的金属杂质离子结合形成配位键,降低它们的化学活性。生长溶液中,杂质的减少,使得晶体生长的表面变得非常"干净",杂质对生长台阶的钉扎效果降低,甚至消失。此时晶体表面生长台阶的聚并程度急剧降低,主要以基本台阶为主,台阶的推移速度也得到大幅度的提高。当溶液中加入过量的CDTA时,其与溶液中的金属杂质离子形成螯合物之后,多余的CDTA会通过氢键的作用吸附在晶体的表面上,弱的氢键使得CDTA一直处于吸附与解吸附的过程中,当其沉积在台阶阵列上时,大的有机分子会形成"山包",这些"山包"不仅会吸附K+、H2pO4-等生长基元,使其难以扩散,而且也会阻碍生长台阶在晶体表面的推移,此时台阶的聚并程度会有所增加,生长速度也相应的减慢。另外,当加入过量的CDTA时,KDP晶体沿X向和Z向的热膨胀系数都降低。4.使用H_3PO_4、KOH调节溶液的pH值,分别采用传统降温法与点籽晶快速法在不同pH值的溶液中,生长了 KDP晶体,利用原子力显微镜观察晶体(100)面的微观形貌和台阶结构,通过激光偏振干涉技术测量了 KDP晶体在不同pH溶液中的生长速度,同时对生长的KDP晶体进行了激光损伤阈值的测试。实验结果表明:在低过饱和度(σ=0.01)下,KDP晶体表面生长台阶的聚并程度随着pH值的降低而减小,尤其是pH=3.5时,生长台阶以基本台阶为主。当溶液的pH值偏离正常值(pH=4.2)时,不论偏高还是偏低,所得到的KDP晶体的激光损伤阈值都有所升高。调高溶液的pH值到5.2时,晶体表面生长台阶上出现突起,这些突起随着过饱和度的增加而变大。晶体的激光损伤阈值先增加后降低,在过饱和度σ=0.04时,达到最大值,约为21J/cm2。调低溶液的pH值到3.5时,随着过饱和度的增加,晶体的生长方式不仅存在螺旋位错台阶同时也存在二维成核生长机制,生长表面上的二维岛不断叠加和堆垛。晶体的激光损伤阈值在过饱和度σ=0.04和σ=0.06时,分别达到最大值和最小值,约为27J/cm2和18.3J/cm2。将溶液的pH值调到pH=2.5时,随着过饱和度的增加,晶体表面生长台阶的聚并程度和阵列宽度都呈现先增大后降低的趋势,台阶的斜率则是呈现先降低后增加的趋势。晶体的激光损伤阈值总体呈现出降低的趋势,其中在过饱和度σ=0.08时出现一个小的波峰,约为22J/cm2。另外,不论调高还是调低溶液的pH值,KDP晶体(100)面的法向生长速度都有所升高。
[Abstract]:With the development of Inertial Confinement Fusion (ICF) engineering, people have put forward higher requirements for the requirements, quality and growth speed of KDP crystals, which can be summed up as "fast, large size, high quality". "Fast": the number of KDP chips needed in the engineering, the growth cycle and the cost are reduced. "Large size". The requirements for crystal size in the ICF system can be met. "High quality": the ICF device can meet the requirements of the KDP crystal performance, such as high laser damage threshold, high transmittance and high optical uniformity. In recent years, the research on the KDP crystal is mainly in the growth process, optical quality, crystal structure and so on. In order to improve the growth speed and optical properties of KDP crystal fundamentally, the micromorphology and growth mechanism of crystal growth should be studied. As a classic aqueous solution growth crystal, temperature, supersaturation, impurity, pH and other medium environment have important influence on the growth habit and optical quality of the KDP crystal. Therefore, this paper is mainly selected. By changing the saturation temperature, supersaturation, pH value, and the doping of metal ions and organic additives, the influence of various medium factors on the micromorphology of the growth steps of KDP crystals and the growth rate are studied. The main contents of this paper are as follows: 1. the KDP crystals were grown at different saturation temperatures and different supersaturation. The laser damage threshold of the crystal was measured. The surface micromorphology of KDP crystals under different conditions was observed by atomic force microscopy. The laser polarization interference system was realized by laser polarization interference system. The relationship between the growth rate and the supersaturation of KDP crystals at different temperatures was measured. The experimental results showed that under low temperature (~35 C C), the growth steps of the crystal surface were in low supersaturation (sigma =0.01), intermediate supersaturation (sigma =0.05) and high supersaturation (sigma =0.08). The average number of the basic steps is 21,22,59 respectively. Correspondingly, the slope of the step also has the peak value under these three supersaturation, which is 9.26 x 10-3,9.64 x 10-3,8.47 x 10-3. respectively. When the high supersaturation is =0.08, the surface of the crystal appears "dendrite" steps. We think there may be a Ehrlich-Schwoebel on the step. E-S) potential barrier. In the medium temperature region (~45 C C, 55 C C), the step aggregation of the crystal surface is peak at the degree of sigma =0.04. At this time, the height of the steps at 45 C C is slightly higher than that of 55 C C. In the process of crystal growth, the slope of the steps appears at a peak in the middle supersaturation region, at 45 C C, the peak of the slope. When the value appears at Sigma =0.06, the corresponding supersaturation corresponding to the peak at 55 C is lower. At the time of sigma =0.04, the step width corresponding to the two peak positions is sharply reduced. At high supersaturation, the coalescence degree and step slope of the steps increase with the increase of supersaturation, which is more significant at 55 C C. At a high temperature region (~65 C) At the same time, the degree of convergence and the slope of the steps of the crystal surface all increase first and then decrease with the increase of supersaturation, all of which appear at the peak of supersaturation Sigma =0.03, at this time the number of the macro steps contains about 48 basic steps, and the slope of the steps is about 8.8 * 10-3. at high supersaturation Sigma =0.08 and sigma =0.09. The "holes" or "holes" appear on the surface of the body. These "holes" are surrounded by the protrusions on the steps. We think these protrusions are produced by the two-dimensional nucleation mechanism. This shows that the growth of the steps is the result of the lapse of the dislocation steps and the two dimensional nucleation mechanism. The.KDP crystal is in a solution of different saturated temperatures. The speed of the lapse is similar with the increase of supersaturation. The supersaturation dead zone in the crystal growth process is sigma D, linear supersaturation sigma, and the extension line is roughly divided into three regions through the critical supersaturation of the origin, V (sigma) curve, and the three supersaturation decreases with the increase of temperature. In addition, the same oversaturation is made. In addition, the step speed increases with the increase of temperature. The laser damage threshold of KDP crystals growing at different saturation temperatures decreases first and then increases with the increase of supersaturation, similar to "V" shape change.2., by doping, to study Fe~ (3+) impurities at different temperatures and supersaturation to KDP crystals. The influence of body growth habit. The micromorphology and growth rate of KDP crystal (100) surface growth step under different conditions were studied by atomic force microscope and laser polarization interference technique. The experimental results showed that the KDP crystal grown by the traditional cooling method, with the increase of Fe~ (3+) doping concentration in the solution, the degree of convergence of the steps and the degree of convergence. The slope ratio increases, the uniformity of the step distribution decreases, the growth dead zone becomes larger and the growth rate decreases. When the concentration of Fe~ (3+) is 30ppm, the growth rate of KDP crystal increases with the increase of temperature. In the high temperature region (~65 C, 75 C C), the growth rate of KDP crystal in the doped solution is faster than that in the undoped solution. In the solution, when the saturation temperature is about 55 C, and the concentration of Fe~ (3+) in the solution is 5ppm, the degree of convergence of the steps of the KDP crystal is higher than the unadulterated condition at low supersaturation (sigma =0.02). At this time, the steps are very straight, the growth is uniform, and many basic steps are shown on the wide step array. When the Fe~ (3+) concentration is 30ppm, The degree of convergence of the steps increases with the increase of supersaturation and is greater than that of the unadulterate at the same supersaturation. When the concentration of Fe~ (3+) is 50ppm, the step is very high at low supersaturation; at the high supersaturation, the step twisting increases, and the.3. is added to the solution, 100ppm, and the organic additive CDTA of 500ppm. The KDP crystal was grown by a point seed rapid method. The effect of CDTA on the surface growth of KDP crystal on the surface of KDP crystal was observed by atomic force microscopy. The step pushing velocity of KDP crystal in CDTA solution with different concentration was measured by laser polarization interference technique. The experimental results showed that CDTA did not advance. In the KDP crystal, the effect of CDTA on the growth of crystal mainly occurs during the diffusion of the growth base element in the solution. The effect of organic additive CDTA on the growth behavior of KDP crystal can be divided into two positive and negative aspects. When a proper concentration of CDTA is added to the solution, it can be combined with the metal impurity ions in the solution. The reduction of impurities in the growth solution makes the surface of the crystal grow very "clean", and the effect of the impurity on the growth step is reduced and even disappeared. At this time, the convergence of the growth steps of the crystal surface decreases sharply, the main step is the basic steps, and the speed of the step is also greatly improved. When an excess of CDTA is added to the solution, after the formation of a metal impurity ion in the solution, the excess CDTA is adsorbed on the surface of the crystal through the action of hydrogen bonds. The weak hydrogen bond makes the CDTA always in the process of adsorption and desorption. When it is deposited on the step array, the large organic molecules will form " The mountain bags "not only absorb the growth elements such as K+, H2pO4- and so on, make it difficult to spread, but also prevent the growth of the steps on the crystal surface. At this time, the degree of convergence of the steps increases and the growth rate slows down accordingly. In addition, when the excess CDTA is added, the thermal expansion coefficient of the KDP crystal along the X direction and the Z direction is reduced by.4.. The pH value of the solution was adjusted by H_3PO_4 and KOH. The KDP crystal was grown in the solution of different pH values by the traditional cooling method and the dot seed crystal fast method. The micromorphology and the step structure of the crystal (100) surface were observed by atomic force microscopy. The growth rate of KDP crystal in different pH solutions was measured by laser polarization interference technique, and the growth rate of KDP crystal in different pH solutions was measured. The laser damage threshold of the growing KDP crystal is tested. The experimental results show that the degree of convergence of the growth steps of the KDP crystal decreases with the decrease of the pH value at low supersaturation (sigma), especially when the pH value is reduced, especially at pH=3.5, the main steps are the basic steps. When the pH value of the solution deviates from the normal value (pH=4.2), it is high or low. The laser damage threshold of the obtained KDP crystal increases. When the pH value of the high level solution reaches 5.2, the surface growth steps appear on the surface of the crystal. These protrusions become larger with the increase of supersaturation. The laser damage threshold of the crystal increases first and then decreases, and the maximum value is reached when the supersaturation is Sigma =0.04, which is about the pH value of the solution of 21J/cm2.. At 3.5, with the increase of supersaturation, the growth mode of the crystal not only has the spiral dislocation steps but also the two dimensional nucleation growth mechanism, and the two dimensional islands on the growth surface are stacked and stacked continuously. The laser damage threshold of the crystal reaches the maximum and the minimum value at supersaturation Sigma =0.04 and sigma =0.06 respectively, which is about 27J/cm2 and 18.3J/cm. 2. when the pH value of the solution is transferred to pH=2.5, with the increase of supersaturation, the convergence degree and the array width of the crystal surface growth step increase first and then decrease, and the slope of the steps decreases first and then increases. The laser damage threshold of the crystal presents a tendency to decrease in general, in which the supersaturation is Sigma =0.08. A small peak, about 22J/cm2, appeared. In addition, the normal growth rate of KDP crystal (100) plane increased with increasing or decreasing the pH value of the solution.
【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O78

【参考文献】