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1、外文资料(一)A look into the futureWith a little imagination, it is not difficult to conjure up visions of future developments in high technology, in whatever direction one cares to look. The following two examples illustrate how advances may take place both by novel applications and refinements of old te
2、chnologies and by development of new ones.(1) Molecular electronicsLithography and thin-film technology are the key technologies that have made possible the continuing and relentless reduction in the size of integrated circuits, to increase both packing density and operational speed. Miniaturization
3、 has been achieved by engineering downwards from the macro to the micro scale. By simple extrapolation it will take approximately two decades for electronic switches to be reduced to molecular dimensions. The impact of molecular biology and genetic engineering has thus provided a stimulus to attempt
4、 to engineer upwards, starting with the concept that single molecules, each acting as an electronic device in their own right, might be assembled using biotechnology, to form molecular electronic devices or even biochip computers.Advances in molecular electronics by downward engineering from the mac
5、ro to the micro scale are taking place over a wide front. One fruitful approach is by way of the Langmure-Biodgett(LB) film using a method first described by Blodgett(1935). A multi-layer LB structure consists of a sequence of organic monolayers made by repeatedly dipping a substrate into a trough c
6、ontaining the monolayer floating on a liquid (usually water), one layer being added at a time. The classical film forming materials were the fatty acids such as stearic acid and their salts. The late 1950s saw the first widespread and commercially important application of LB films in the field of X-
7、ray spectroscopy (e.g,Henke 1964,1965). The important properties of the films that were exploited in this application were the uniform thickness of each film, i.e. one molecule thick, and the range of thickness, say from 5to 15nm, which were available by changing the composition of the film material
8、. Stacks of fifty or more films were formed on plane of curved substrates to form two-dimensional diffraction gratings for measuring the characteristic X-ray wavelengths of the elements of low atomic number for analytical purposes in instruments such as the electron probe of X-ray micro-analyzer.(2)
9、 Scanning tunneling engineeringIt was stated that observational techniques such as microscopy do mot, at least for the purposes of this article, fall within the domain of nanotechnology. However,it is now becoming apparent that scanning tunneling microscopy(STM) may provide the basis of a new techno
10、logy, which we shall call scanning tunneling engineering.In the STM, a sharp stylus is positioned within a nanometre of the surface of the sample under investigation. A small voltage applied between the sample and the stylus will cause a current to foow through the thin intervening insulating medium
11、(e.g.air,vacum, oxide layer). This is the tunneling electron current which is exponentially dependent on the sample-tip gap. If the sample is scanned in a planr parallel to ies surface and if the tunneling current is kept cnstant by adjusting the height of the stylus to maintain a constant gap, then
12、 the displacement of the stylus provides an accurate representation of the surface topographyu of the sample. It is relevant to the applications that will be discussed that individual atoms are easily resolved by the STM,that the stylus tip may be as small as a single atom and that the tip can be po
13、sitioned with sub-atomic dimensional accuracy with the aid of a piezoelectric transducer.The STM tip has demonstrated its ability to draw fine lines, which exhibit nanometre-sized struture, and hence may provide a new tool for nanometre lithography.The mode of action was not properly understood,but
14、it was suspected that under the influence of the tip a conducting carbon line had been drawn as the result of polymerizing a hydrocarbon film, the process being assisted by the catalytic activity of the tungsten tip. By extrapolating their results the authors believed that it would be possible to de
15、posit fine conducting lines on an insulating film. The tip would operate in a gaseous environment that contained the metal atoms in such a form that they could either be pre-adsorbed on the film and then be liberated from their ligands or they would form free radicals at the location of the tip and
16、be transferred to the film by appropriate adjustment of the tip voltage.Feynman proposed that machine tools be used to make smaller machine tools which in turn would make still smaller ones, and so on all the way down to the atomic level. These machine tools would then operate via computer control i
17、n the nanometre domain, using high resolution electron microscopy for observation and control. STM technology has short-cricuired this rather cumbrous concept,but the potential applications and benefits remain.展望未来不论在什么方面展望,想象未来高科技发展是很容易的。以下两个例子阐述了通过旧技术的改进和新技术采用可以使科技取得新的进展。( 1 )分子电子学光刻和薄膜技术是关键技术,有可能
18、持续和缩小集成电路的规模, 为了增加包装密度和运行速度。小型化已取得了从宏观到微观规模的向下工程。由简单外推法,将会采取将近两个几十年来通过电子转换来减少分子尺寸。分子生物学和基因工程的影响提供了一个刺激,从而使工程师向上思考,开始将单分子概念,瓦赫代理作为一个电子装置来思考,这样可能会使生物技术形成分子电子器件或甚至生物芯片的电脑。分子电子学优势从宏观到微观的各个领域都在体现。一个卓有成效的方法,是透过该langmure - biodgett (磅)电影使用的一种方法由blodgett所描述的( 1935年)来实现 。多层磅的结构组成一个序列的有机单分子膜通过多次浸渍,包含漂浮在液体中的单层(通常是水) , 一层在同一时间补充。经典电影形成的材料都是不饱和脂肪酸,如硬脂酸及其盐类。 50年代后期看到的第一广泛和具有重要商业价值的应用LB膜在该领域的X射线光谱(例如, henke 1964,1965 ) 。薄膜的重要性能被剥削,在这方面应用统一的厚度,即一个分子厚,厚度的范围从5to 15nm ,其中可通过改变薄膜材料的组成。成堆的五十或以上的薄膜上形成的平面基板弯曲,形成两个空间为衍射光栅测量特征,低原子序数的各项要素的X射线波长为分析目的,如电子探针X射线微型分析器。( 2 )扫描隧道工程据指出,观测技术,如显微镜不能属于该域的纳米技术,至少为
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