Nanofabrication on gold surface with scanning tunneling microscopy

We have developped an experimental technique for writing stable features on an atomically flat gold (111) surface with Scanning Tunneling Microscope (STM). By applying voltage pulses (close to 3 V) across the tunneling junction in controlled atmosphere with the presence of water or ethanol vapour, nano-hole can be produced. The smallest hole formed is 3 nm in diameter and 0.24 nm in depth. This nano-hole represents the loss of about 100 Au atoms in the top atomic layer of gold surface, there is no atomic perturbation seen inside and outside the nano-hole. Different nanostructures (lattice of dots, legends, map, etc.) are fabricated. We report the dependence of the threshold voltage for the formation of a nano-hole on the relative humidity and the existence of a “critical humidity”. Different tips (Pt---Ir, Au, Au---Pd, Ag and W) are used, the relationship between the threshold voltage and the relative humidity is basically independent of the tip material. We approve that the mechanism involved in pit formation could be electrochemical in origin.     

Localization of lectin receptors on the surface of C1300 neuroblastoma cells

D-mannose, D-galactose, N-acetyl-D-galactosamine, N-acetyl-D-glucosamine and L-fucose which are sugar determinants of receptors were found on the surface of neuroblastoma cells by means of four carbohydrate-specific lectin groups. Labeling of lectins was performed by horseradish peroxidase, ferritin and colloidal gold. Peculiarities of the lectin receptors distribution on the surface of immature neuroblastoma cells were detected.     

Location of peptidoglycan and teichoic acid on the cell wall surface of Staphylococcus aureus as determined by immunoelectron microscopy.

Anti-peptidoglycan (PG) and anti-teichoic acid (TA) antibodies were prepared from sera of rabbits immunized with the cell wall fraction of Staphylococcus aureus Cowan I by the specific adsorption technique with purified teichoic acid or peptidoglycan. The anti-PG antibody recognized the trichloroacetic acid-treated walls (TCA wall) prepared from S. aureus, Bacillus subtilis, and Micrococcus luteus but did not react with teichoic acid or proteins extracted from the cell wall of Staphylococcus. The anti-TA antibody specifically reacted with cell wall teichoic acid of beta-type sugar configuration. The reaction sites of these antibodies on the cell wall of S. aureus Wood 46 were determined by immunoelectron microscopy using colloidal gold as a probe. The anti-TA antibody reacted mostly with the fibrous electron-dense mass on the cell surface. The reaction was also seen on the inner surface of the cell wall. The anti-PG antibody reacted with the fibrous structures and also directly on the cell wall surface. The distribution of the probes on the cell wall surface examined with the scanning electron microscope showed that there was no localized distribution in respect to the cell division. We knew from these observations that the external surface of the cell wall of Staphylococcus is covered with the fibrous mass which consists mostly of teichoic acid but partially of peptidoglycan.     

Immunoelectron microscopic study of the opsin distribution in the photoreceptor cells of Drosophila melanogaster.

Distribution of opsin in the compound eye of Drosophila melanogaster was examined by post-embedding immunoelectron microscopy using a monoclonal antibody against the Drosophila Rh1 opsin and gold-conjugated secondary antibody. Numerous gold particles were observed on the rhabdomeric microvilli of R1-R6 retinular cells. In the retinular cell body, gold particles were distributed in rough endoplasmic reticulum, subrhabdomeric cisternae (SRC), multivesicular bodies, and secondary lysosomes. In the rdgA mutant, whose SRC are absent, density of gold particles on the rhabdomeric microvilli was about 20% of normal. These results suggest the involvement of SRC in opsin transport.     

On the modification of a silicon surface studied by scanning tunneling microscopy

The results of investigating the surface of Si with a thin oxide layer by scanning tunneling microscopy in air are reported. The tunneling current is shown to represent a superposition of several components. This circumstance makes it possible to suggest that a pseudoprofile is detected instead of the true surface image. The principal laws in modifying the pseudoprofile are established. In the case of positive or negative polarity of a sample, the image is observed in the form of indentations or protrusions, respectively. The electron nature of the modification under observation is suggested, and this suggestion is corroborated by the possibility of implementing write-erase-write cycles for the image of the same surface section. The mechanism of modifying the Si surface is discussed for the model of the insulator-oxide-semiconductor structure, in which an adsorbate layer may serve as an insulator.     

Influence of interface traps and surface mobility degradation on scanning capacitance microscopy measurement

Although scanning capacitance microscopy (SCM) is based on the MOS capacitance theory, the measurement frequency is 915-MHz instead of 100 kHz to 1 MHz in conventional MOS capacitance-voltage measurement. At this high frequency, the reactance of the probe tip-to-substrate capacitance can become smaller than the series resistance of the substrate inversion layer, particularly when the surface mobility is degraded. The response of the oxide-silicon interface traps to SCM measurement is also different due to the use of a 10-kHz signal to determine dC/dV. In this paper, we compare experimental and simulation data to demonstrate the effects of interface traps and surface mobility degradation on SCM measurement. Implications on the treatment of SCM data for accurate dopant profile extraction are also presented.     

Detection of iron-oxide layer on the surface of iron nitride using high-resolution electron microscopy and Fourier filtering

High-resolution electron microscopy (HREM) was used to detect the surface Fe3O4 iron-oxide layer formed on [011] Fe4N iron nitride due to electron irradiation in the transmission electron microscope. The existence of a surface oxide layer was confirmed by both image processing and through-focus observation. Images of the iron oxide were revealed using the process of fast Fourier transformation (FFT) of experimental HREM images, filtering of the FFT patterns and inverse FFT. By through-focus observation, HREM images of iron oxide were obtained based on the tuning of contrast transfer function. Fourier filtering is effective for examining the beginning of phase transformation, because at this stage the diffraction spots of iron oxide are too weak to be detected. At the time when the iron oxide layer has developed to some extent, through-focus observation is useful to obtain an image of oxide layers.     

半金属表面上酞菁锰分子的转动态研究

利用低温STM研究了半金属Bi(111)表面上单个酞菁锰分子的转动态。通过高分辨STM图发现,在液氮温度(77K)下单个酞菁锰分子呈六角形。利用STM操纵技术实现了对单个酞菁锰分子的制动,并通过对单分子的高低起伏和吸附构型分析,确定分子在Bi(111)表面做非连续的中心转动。这种单分子转动是三种相对稳定的吸附构型交替变化的结果。结合I-t谱技术,进一步验证了这三种分子吸附构型的存在;并利用近似统计分析方法得到三种吸附构型各自出现的概率以及其相对能量。     

Study of the properties of the surface of gallium arsenide by scanning atomic force microscopy

Using the method of atomic force microscopy, complex studies of the profile, potential distribution φ(x,y), and distributions of the phase contrast of the surface of n-GaAs subjected to various types of chemical treatment are carried out. The distribution of the potential and phase contrast at a microlevel, in general, correlates with the profile character. The surface treated in the solution H₂SO₄: H₂O = 1: 10 is characterized by a high degree of nonuniformity with an average roughness of the main profile Δh≈ 10 nm. A considerable part of the surface is covered by hills 20–60 nm in height and 100–500 nm in diameter forming a specific substructure, which correspond to potential jumps as large as 50–60 mV against a general background of 0.77–0.80 V. At a nanolevel, correlation between the profile and phase contrast is clearly pronounced, but no correlation is found between the profile and potential distribution. Treatment of the surface of n-GaAs in a concentrated aqueous NH₄OH solution leads to a decrease in the value of φ(x,y) by ～0.2 V, and in its roughness by more than an order of magnitude (～0.75 nm). The distribution of the profile and phase contrast over the surface is close to the ideal Gaussian distribution for relatively small areas of the surface (200 × 200 nm²). As the area increases, deviation from the Gaussian distribution becomes substantial because of smooth variation in the potential over the contact area. Conservation of the Gaussian character of the surface profile and a simultaneous rise in the average level of the roughness with an increase in the analyzed area indicates the fractal mechanism of formation of the surface profile.     

福氏2a痢疾杆菌膜抗原的免疫电镜定位

本文报告应用抗福氏2a痢疾杆菌膜成份McAb及胶体金探针对细菌膜抗原进行了定位。结果显示4种抗脂多糖McAb(3A6、2E6、4F1、2A3)可不均一的识别位于细菌壁表面的抗原,而另外一种抗LPS的McAb种(1G8)和一种抗膜蛋白McAb(1A1)识别的抗原未暴露于细菌表面。应用细菌膜碎片包埋前染色成功定位了抗膜蛋白McAb(1A1)位于细菌内膜的抗原。与McAb的生物活性比较表明阳性标记细菌表面抗原的McAb的抗原与其阻段志贺氏菌接触性溶血试验和对小鼠的被动保护力密切相关。提示免疫电镜标记技术确定LPS抗原表位在细菌表面的可及性和拷贝数对构建和筛选痢疾工程菌苗具有重要意义。     

Scanning electron microscopy used to measure the feature dimensions of a nanoscale test pattern on a silicon surface

A method is proposed for nanoscale dimensional metrology with the scanning electron microscope in the case of an array of trapezoidal ridges on a silicon surface, the minimum feature size being comparable with the effective beam diameter. The method is tested by measuring the top width of an individual ridge, which lies between 14 and 24 nm. The method works at accelerating voltages higher than 15 kV.     

Study of the surface structure of tin dioxide layers for gas sensors by atomic-force microscopy

This paper presents the results of a study by atomic-force microscopy of tin dioxide layers as a function of the conditions under which they are doped with iodine and tellurium during the production of the layers by thermal vacuum deposition of tin, followed by oxidation. Data concerning the atomic-force microscopy of layers fabricated in various processing regimes are presented and discussed. It is shown that introducing volatile impurities into the starting charge is an effective means of modifying the surface structure of the layers and of altering the character of its microsurface. The temperature dependence of the sensitivity of the layers to toluene vapor is studied and analyzed. Fiz. Tekh. Poluprovodn. 32, 654–657 (June 1998)     

Quantitative evaluation of the surface membrane receptors of leukemic cells to blood serum transcobalamin-II

Serum protein transcobalamin II (TC-II) is responsible for transport of cobalamins into mammalian cells. A method of quantitative estimation of plasma membrane receptors of hemopoietic cells to TC-II cobalamin complex is suggested. Analysis of mouse leukemia L1210 cells includes the saturation of radiolabelled ligand-receptor complex with papain. The number of receptors and 57CoCNCbl content in one cell is determined by differentiated radioactivity count of solubilized protein complexes and of cytoplasm.     

Immunoelectron microscopy of Proteus vulgaris by the plasma polymerization metal-extraction replica method: differential staining of flagellar (H) and somatic (O) antigens by colloidal golds

Flagellar (H) and somatic (O) antigens of Proteus vulgaris were differentially stained with antibodies coupled to different sizes of colloidal gold particles, and the distribution of these antigens was visualized by the plasma polymerization metal-extraction replica (PMR) method. The H antigen, labeled with 5 nm colloidal gold, was almost exclusively located on the flagella, whereas the O antigen, labeled with 10 nm colloidal gold, was almost exclusively located on the bacterial body. The marker gold particles were clearly observed as electron-dense particles on the relatively low contrast background of three-dimensional replica image of the flagellated bacteria. Thus, the PMR method may prove to be a useful tool for studying the localization of multiple substances on the cell surface, at a high resolution and in three dimensions. The diameter of the flagella measured by the replica method was about 15 nm, close to the value obtained by negative staining (16 nm). When treated with anti-flagellar (H) factor serum and protein A-gold, the diameter of flagella was significantly increased to about 35 nm. This increase in diameter was presumably caused by binding of immunoglobulins to H antigens of flagella.     

Evaluation of the distribution of lectin receptors on the surface of tumor and transformed cells using methods of variation statistics

Statistical procedures were used to estimate lectin receptor distribution on the surface of ascite lymphoma cells, neuroblastoma C-1300 cells and of transformed human T- and B-derived lymphoid cell lines. Relationships between the arithmetic means and mean square variances for sample populations from each cell and ferritin- or colloidal gold-lectin combination were used to define four types of topographical distributions: uniform-ordered, uniform-random, random and clustered.     

脊髓前角运动神经元GR受体免疫电镜观察

近年肾上腺皮质激素的糖皮质激素受体 ( Glucocorticoid receptor.GR)在脑神经细胞分布与作用的研究已倍受关注[1] ,脊髓 GR受体的分布尚未见报道 ,本研究采用免疫组织细胞化学方法对 GR受体在脊髓前角运动神经元的超微结构定位进行了电镜观察 ,为进一步探讨 GR受体对脊髓功能的作用机制提供形态学依据。材料与方法　实验动物为成熟 Wistar大鼠 (体重 2 5 0～ 30 0 g) ,全身麻醉下 ,用 4%多聚甲醛( 0 .1 mol/ L PBS缓冲液配制 )固定液心脏灌流固定 ,摘出脊髓 ,用同种固定液再继续浸泡固定一夜 ,同上缓冲液洗净标本 ,采用 microslicer(…     

Growth of silicon nanowires on H-terminated Si {111} surface templates studied by transmission electron microscopy

We have studied the growth of silicon nanowires (SiNWs) by means of transmission electron microscopy. SiNWs are grown from nanocatalysts via the Vapor-Liquid-Solid (VLS) mechanism using silane (SiH4) gas as a source gas. The nanocatalysts are prepared on a hydrogen (H)-terminated Si surface. We have examined the formation mechanism of nanocatalysts on H-terminated surface and have observed several structural variants of SiNWs. According to the study we have suggested that many structural variations of SiNWs are possible, which modify the structural properties of SiNWs to great extents.     

Comparative study of the lymphocyte surface receptors isolated from the blood and tissue of malignant tumors

Comparative investigation of subpopulations and functional properties of lymphocytes isolated from the tumour tissue (TTL) as well as of lymphocytes of the peripheral blood (PBL) of 11 lung cancer patients and 18 breast cancer patients has shown that an increase in the quantity of theophylline-sensitive cells (suppressors and killers) is characteristic of TTL. After 20 hours of incubation of the mixture of the studied lymphocytes and sheep erythrocytes at 4 degrees C an increase in the number of E-RFC proved to be more intensive for TTL than for PBL. The result obtained may suggest the blocking of the superficial receptors of TTL to sheep erythrocytes.     

Distal surface of the rat ruffle-ended ameloblasts at the stage of enamel maturation observed by scanning electron microscopy

Distal surface of the rat ruffle-ended ameloblasts was observed by high resolution scanning electron microscopy. Specimens fixed by perfusion with 0.5% formaldehyde and 0.5% glutaraldehyde were decalcified with ethylenediamine tetraacetic acid and freeze-fractured using dimethyl sulfoxide. They were treated with 0.1% osmium tetroxide for 96 hr to remove excess cytoplasmic matrices, dehydrated, and critical-point dried. The present method was useful for observing both surface and intracellular structures simultaneously. The dense lamina lining the distal surface of the ruffle-ended ameloblasts having been dissolved in this preparation, the surface was clearly demonstrated in three dimensions under SEM. The surface was characterized by a complex labyrinth formed by protrusion and invagination of the plasma membrane. At high magnification, two kinds of minute granules are visible: small and larger granules measured as 10-20 nm and 70 nm in diameter, respectively. The former were more numerous than the latter. Furthermore, microfibrils connecting the protrusions of the plasma membrane were observed on the distal surface. The small granules probably connect the dense lamina with the distal surface of the ameloblasts. In addition, a denuded area free from the granules was sometimes recognized on the distal surface. These surface structures of the distal end of the ameloblasts appeared to be concerned with the enamel maturation.