图1 扫描透射电子显微像(STEM)形成示意图[6]

Fig. 1 Schematic diagram for the formation of STEM image[6]

图2 (a)样品的原子柱二维投影(Si〈110〉方向)、(b)样品高角散射时的钉状物体势函数和(c)实验像强度分布解释为物体的势函数与电子束斑强度函数的卷积[8]

Fig. 2 Potential for high-angle scattering of Si atomic columms The specimen in (a) consists of an array of atomic columns (〈110〉 Si for example), in which the potential for high-angle scattering can be represented by an object function consisting of weighted spikes, as shown in (b). The experimental image can be interpreted as a convolution of the experimental probe and the object function, as in (c)[8]

图3 扫描透射电子显微镜(VG Microscopes HB501UX STEM 工作电压100 kV, 电子束斑尺寸 ~ 0.22 nm)在(a)相干和(b)非相干成像条件下的不同衬度传递函数 [6]

Fig. 3 Different contrast transfer functions of a STEM (VG Microscopes HB501UX STEM operated at 100 kV with a probe size of ~ 0.22 nm) measured simultaneously at (a) coherent and (b) incoherent imaging conditions by using a small bright field detector and a large annular detector, respectively Plots show the very different transfer functions for the two detectors, the bright field detector showing contrast reversals and oscillations characteristic of coherent phase contrast imaging, the dark field detector showing a monotonic decrease in transfer with spatial frequency characteristic of incoherent imaging[6]

图4 球差校正器及其对Z-STEM像分辨率的改善[11]

Fig. 4 Aberration corrector and improvement of Z-STEM image resolution [11] (a) An Aberration corrector consisting of 60 optical components, (b) experimental Z-STEM image of Si in [110] orientation taken from VG STEM HB501 STEM with a point resolution of ~ 0.2 nm, un-resolving the dumbbell structure of silicon, and (c) Z-STEM image of Si in [110] orientation taken from VG STEM HB501 STEM equipped with Nion aberration corrector, resolving clearly the dumbbell unit structure of silicon with a point resolution of 0.13 nm and increasing the ratio of signal-to-noise

图5 (a) Si/HfO2堆垛结构的剖面Z-STEM像, HfO2/SiO2的界面结构见图的中心部分[16], (b)沿Si衬底[110]方向观察HfO2/HfSiO堆垛结构的剖面HRETM像和(c)相同堆垛结构的剖面Z-STEM像[17]

Fig. 5 Images of Si/HfO2 (a) and HfO2/HfSiO (b,c) gate stacks (a) Cross-sectional Z-STEM image of an Si/HfO2 gate stack. The SiO2/HfO2 interface is seen in the center of the image[16]; (b) Cross-sectional HRTEM image of a HfO2/HfSiO gate stack viewed from the [110] direction of Si substrate, and (c) HAADF image of the same stack[17]

图6 Si(111)衬底上外延生长的Pr2O3薄膜剖面HRTEM像,在Pr2O3薄膜上又外延生长Si (111)薄膜[20]

Fig. 6 Cross-sectional HRTEM image of the epitaxial Pr2O3 film (6 nm thick) grown on Si(111) substrate, and the film can be overgrown epitaxially with high quality Si (111) film[20]

图7 (a) a-Si/Y2O3/c-Si(单晶硅)堆垛结构的Z-STEM像。由于Y2O3薄膜暴露到在大气中, 在Y2O3/c-Si衬底的界面处形成SiOxHy界面反应层, 如图中虚线标注所示; (b) 相同堆垛结构的剖面Z-STEM像, 但Y2O3薄膜在沉积过程中原位覆盖一层非晶硅层(a-Si), 在Y2O3/Si界面处就观察不到SiOxHy反应层[21]

Fig. 7 Z-STEM image of a-Si/Y2O3/c-Si stack (a) The formation of SiOxHy interfacial layer was due to the exposure of Y2O3 film to atmospheric conditions; (b) The interfacial layer of SiOxHy was not visible due to the Y2O3 film in-situ capped by a layer of amorphous Si during the deposited process[21]

图8 Si(001)衬底上分子束外延生长的SrTiO3薄膜剖面HRTEM像, 显示在SrTiO3薄膜和Si衬底之间形成原子级锐变的界面[23]

Fig. 8 Cross-sectional HRTEM image of a SrTiO3 film epitaxially grown on Si (100) substrate by MBE, showing the formation of an atomically abrupt crystalline interface between the SrTiO3 and Si[23]

图 9 (a)外延Si/LaAlO3界面的HRTEM像, (b) HAADF-STEM像, 该图像表明界面具有一个3 × 1 的界面重构(即每3个La原子中间就有一个La原子在界面处消失)和(c)基于界面结构的Z-STEM像构筑的Si/LaAlO3界面结构模型[25]

Fig. 9 (a) HRTEM and (b) HAADF-STEM images from an epitaxial Si/LaAlO3 interface showing an interface reconstruction where every third La column is missing at the interface. (c) Interface models based on the HAADF-STEM images[25]

图10 不同退火温度下,原子层沉积(ALD)法生长的HfO2薄膜与TiN金属栅电极及Si衬底之间的界面结构的Z-STEM像[26]

Fig. 10 Z-STEM images of the HfO2 gate dielectrics grown by atomic layer deposition on Si substrates and their interfaces with TiN electrodes and silicon, annealed at (a) 800℃ and (b) 900℃[26] The dashed lines are a guide to the eye to indicate the approximate position of the interfacial layer. Note the roughening of interfaces after annealing at 900℃

图11 Hf 原子在Si/SiO2/HfO2 堆垛器件中的三维分布[30]

Fig. 11 Three-dimensional locations of single Hf atoms in a Si/SiO2/HfO2 stacked device[30] (a) A schematic view diagram of the Si/SiO2/HfO2 stacked device with a SiO2 layer shown in red and the alternative dielectric, HfO2 shown in yellow color, where S and D representing the source and drain, respectively. (b) Three ADF images of the stack is represented by slice views in planes of x-y, x-z, and y-z, respectively. One isolated single Hf atom is marked the white circles. This representation demonstrates that the Hf atom is located inside the TEM sample. (c) A 3D reconstruction of part of the HfO2/SiO2/Si interface structure showing single Hf atoms. The Si substrate was color coded in gold, whereas the HfO2 film is marked solid yellow. Single Hf atoms with different positions within the interface layer are coded separately in green, black, red, and blue colors, respectively