Investigation on the scattering effect of ceramic Nd:YAG

This paper investigates the scattering effect of domestic 0.5 at{\%} ceramic Nd:YAG. An effective method has been utilized to measure the scattering and absorption coefficients. An end-pumped continuous wave (CW) Nd:YAG ceramic laser was also demonstrated. A maximum output power of 6.7~W at 1064~nm was obtained at an 808-nm pump power of 32.9~W. Conversion efficiency and slope efficiency have been achieved. This indicates that scattering has an important effect on the optical performance of ceramic Nd:YAG.     

微波等离子体下GaN的分解与纳米金刚石膜的沉积

采用微波等离子体化学气相沉积(microwave plasma chemical vapor deposition,MPCVD)技术系统地研究了GaN的分解机制.结果表明微波等离子体富氢环境促进了GaN的分解反应,分解过程由表面缺陷开始,向侧面扩展,最后沿氮极性面进行;氢等离子体中通入少量氮气能够显著抑制GaN的分解,在此基础上采用两步生长法成功实现在GaN上纳米金刚石膜的直接沉积.     

氢终止金刚石表面的形成机理

为考察金刚石形成氢终止表面的反应机制,采用微波氢等离子体处理以及电阻丝氢气气氛加热处理进行对比研究.利用光发射谱(OES)和漫反射傅里叶变换红外光谱(DRIFTS)分别表征了微波氢等离子体中的活性基团和金刚石表面氢终止浓度.结果表明,微波氢等离子体环境下,随着衬底温度、等离子体密度和能量的增加,温度至700 ℃ (800 W/3 kPa)时,等离子体中出现了明显的CH基团;相应地,金刚石表面氢终止浓度随温度、等离子体密度和能量的增加而增加.采用氢气气氛下电阻丝加热的方法同样形成了氢终止金刚石表面,表明微波等离子体处理金刚石表面形成氢终止主要源于由温度控制的表面化学反应,而非等离子体的物理刻蚀作用.氧终止金刚石表面形成氢终止的机制是表面C=O键在高于500 ℃时分解为CO,相应的悬挂键由氢原子或氢分子占据.     

电弧分区特征对金刚石形核的影响

在直流电弧等离子体喷射CVD法制备金刚石膜中,电弧可分为弧心、弧干、弧边三个区域.本文主要阐述了电弧的分区特征,讨论电弧区域特征对金刚石形核的影响.同时,以电弧分区特征为基础,探讨了预处理方式和温度对金刚石形核的关联影响.结果表明:形核初期对应于TiC粉的Raman谱,衬底的钛过渡层表面形成了TiC的过渡层,弧心区域金刚石形核迅速,形核密度较高,而在弧边区域金刚石形核缓慢,形核密度相对较低.     

Behaviour of Self-Standing CVD Diamond Film with Different Dominant Crystalline Surfaces in Thermal-Iron Plate Polishing

Self-standing CVD diamond films with different dominant crystalline surfaces are polished by the thermal-iron plate polishing method. The influence of the dominant crystalline surfaces on polishing etfficiency is investigated by measuring the removal rate and final roughness. The smallest rms roughness of 0.14 μm is measured with smallest removal rate in the films with the initial （220） dominant crystalline surface. Activation energy for the polishing is analysed by the Arrhenius relation. It is found that the values are 170kJ/mol, 222kJ/mol and 214kJ/mol for the film with three different dominant crystalline surfaces. Based on these values, the polishing cause is regarded as the graphitization-controlling process. In the experiment, we find that transformation of the dominant crystalline surfaces from （111） to （220） always appears in the polishing process when we polish the （111） dominant surface.     

直流电弧等离子体喷射化学气相沉积高质量金刚石膜残余应力分布的拉曼谱分析

不同工艺条件下在钼衬底(φ60mrn)上用100kW直流电弧等离子体喷射化学气相沉积设备进行金刚石膜的制备。金刚石膜用扫描电镜(SEM)、拉曼谱(激光激发波长为488m)和X射线衍射来表征。研究结果表明，在直流电弧等离子体喷射化学气相沉积金刚石膜的过程中，内应力大小从金刚石膜的中央到边缘是增加的，并且应力形式是压应力。这说明了在金刚石膜中存在明显的应力不均。甲烷浓度和衬底温度都影响金刚石膜中的内应力。随着甲烷浓度和衬底温度的提高，金刚石膜中的内应力呈增加的趋势。     

基于荧光玻璃的高效LED白光技术

采用高温熔融法制备了一定质量比例的SiO_2-YAG∶Ce~(3+)片状荧光玻璃,厚度为0.2 mm,分析其XRD物相、光学和SEM微观结构、PL光谱。结果表明:荧光玻璃保留了晶相,荧光粉颗粒在玻璃基质中均匀分布,荧光玻璃和荧光粉的激发响应关系一致。在465 nm蓝光激发下,发射波长均在535 nm附近,表明荧光玻璃除含有玻璃相,还有荧光粉的物质结构特性。将不同波长蓝光芯片与不同荧光粉含量的荧光玻璃进行封装测试,结果表明:器件的流明效率可达到234.81 lm/W;色温和显色指数均随荧光粉含量增加而单调下降,呈现高色温和低显色指数;荧光粉质量分数从6%增加至15%时,不同波长激发下的色坐标x与y呈现大致相同的线性变化率。采用450 nm激光激发荧光玻璃,测试样品温度变化发现温升较缓,温降迅速,耐热性能优越。实验结果表明,将荧光玻璃用于LED白光照明封装,能实现流明效率和耐热性能的大幅提升,形成良好的白光输出。     

Sixth harmonic generation of 1064-nm laser in KBBF prism coupling devices under two kinds of gas conditions

The conversion efficiency on the sixth harmonic of 1064 nm in KBe2BO3F2 （KBBF） at different gas pressures in two kinds of gases, helium and nitrogen, is measured and compared. In the both gases, maximum conversion efficiency on the sixth harmonic of 1064 nm in high vacuum is nearly 10% of 355 nm, which is almost four times higher than that in low vacuum. The maximum average output power at 177.3 nm is 670 ttW with the repetition rate of 10 Hz and the duration of 20 ps in high vacuum. It indicates that the sixth harmonic generation in high vacuum is more preferable than that in low vacuum.     

用镀有钛过渡层的钼衬底制备无裂纹自支撑金刚石膜

为了解决金刚石膜脱膜开裂的问题,尝试了一种复合衬底,即镀有钛过渡层的钼衬底.利用直流等离子体喷射法在复合衬底上制备了不同厚度无裂纹的自支撑金刚石膜.用扫描电镜(SEM)、拉曼谱和X射线衍射表征金刚石膜的特征,并检测了其断裂强度.结果表明,用复合衬底制备的金刚石膜在950℃具有最小半高宽,在实验温度下所获得的金刚石自支撑膜的断裂强度均超过了500MPa.