任何一种化学元素的用途的介绍!英文最好……

任何一种化学元素的用途的介绍!英文最好……
任何一种化学元素的用途的介绍!英文最好……

任何一种化学元素的用途的介绍!英文最好……
纭匋br/>Silicon as a material in microelectronics
Microelectronics is probably the most important achievement of our time,comparable with the invention of letterpress in the 16th,the invention of the stean engine in the 18th or the invention of the electricity in the 19th century,respectively.If nowadays one is talking about "scientific revolution",the term microelectronics is inevitable.The technologies associated with the headwords "Internet" and "data highway" wouldn't be conceivable without the invention of the transistor by Bardeen and Brattain.Although the first transitors were realized with germanium,todays microelctronics technology is dominated by exclusively one material:silicon.In fact,some materials have better properties,for instance,gallium arsenide (GaAs),but there are many reasons why silicon is the material of choice:
Silicon is the second frequent element on the earth,the accessible part of the earth consists of 27.5% of this element (predominatly as silicondioxide,SiO2)
Silicon crystal growth technology is the most evolved one regarding purity,crystal defects (i.e.dislocations) and size (the industry is now starting to develop technologies for processing 12 inch wafers,i.e.single crystals with a diameter of a long playing record)!
It is possible and easy to grow a stable passivation layer of SiO2 on the silicon surface,a very important point regarding the processes in microelectronics,like photolithography or field and barrier oxides for transistors,for instance.
On the other hand silicon is also a very intersting material for electrochemists,as we will see in the next paragraph.
Silicon as a material in electrochemistry
Bardeen and Brattain,even though for a different purpose,have probably performed the first electrochemical experiments with semiconductors.Meanwhile semiconductor electrochemistry is a well established,independent scientific reasearch area.Especially the silicon/hydrofluoric acid contact shows very interesting behaviour,which is not quite well understood:
Anodic dissolution with formation of anodic oxides (electropolishing)
Current and voltage oscillations
Anodic dissolution with porous silicon formation
The last part of this short introcution will focus on the last-mentioned material,porous silicon.
A "new material":Porous silicon
The first observation of porous silicon layers goes back 40 years and was done by Uhlir and Turner.Though,they interpretated the black/brown coloured surface as precipitation of silicon related species from solution.Today it is generally accepted,that porous silicon formation is an etching process,where Si-atoms are dissolved from the bulk material and the original crystal structure remains uneffected.
Dependent on the experimental conditions (doping density of bulk material,electrolyte concentration,current density,etchung voltage,temperature) different modifications of porous silicon can be formed,which make it necessary to introduce a classification of the different pore types.With this different pore etching techniques it is now possible to vary not only the electronical but also the mechanical properties of silicon in a scale from millimetres to nanometres.
Nanoporous silicon
One of the remarkeble features of nanoporous silicon is its unusual optical properties.The nanoporous structures have dimensions in the low nm-range.If the structure size reaches a value below,say 3 nm,quantum effects can occur and therefore nanoporous samples can exhibit strong visible photoluminescence and electroluminscence,as can be seen in the picture below.
Photoluminescence of a nanoporous silicon sample
This is why the material is very interesting for applications in optoelectronics,because then it will be possible to integrate optoelctronical devices directly on silicon substrates!
Macroporous silicon
Another very promising material is macroporous silicon,which can be obtained only on n-type bulk material.The principle of macropore etching was predicted by Föll and Lehmann,who suggested to use backside illumination for pore growth.In contrast to the commonly used front side illumination for PS formation on n-type silicon,where holes,which are essential for silicon dissolution,are generated close to the sidewalls of the pores,the backside illumination has a tremendous advantage.The holes supplied at the back side of the wafers have to reach the silicon/electrolyte interface by diffusion.Because the front side of the wafer is in the dark and therefore in depletion,the holes will preferently reach depressions or pits,where the electrical field is enhanced and promote dissolution there.With this technique it is possible to create pores (or better:trenches) with diameters in the µm range and lengths of several hundred microns up to wafer thickness!Two examples for macropores are shown in the figures below.
Examples for macropores in n-type silicon
Meanwhile this material is the first out of the different types of porous silicon that has found commercial applications in capacitor technology.In addition,some more possible and partly realized applications of commercial as well as academic interests are worth to mention:
Microsystem technology
ink jet nozzles
channel plates
three dimensional microstructuring of silicon with high aspect ratios
Photonic bandgap material
Defined model (porous) electrodes in semiconductor electrochemistry

氢元素周期表中第一号元素，位於第一周期I A 族。
16世纪未，瑞士的著名医生帕拉塞斯用铁屑和酷酸反应得到一种可燃性气体。17世纪时，你蒙特和波叉耳曾在实验中偶然接触到它，英国化学家卡文迪许对氢的出现和研究作出了突出贡献，他最先收集并仔细研究了氢气的性质。1766年卡文迪许把一篇名为(人造空气的实验)的研究报告提交给英国 皇家学会。有关氢气的议述主要：
1. 制取可燃性空气意指只限...

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氢元素周期表中第一号元素，位於第一周期I A 族。
16世纪未，瑞士的著名医生帕拉塞斯用铁屑和酷酸反应得到一种可燃性气体。17世纪时，你蒙特和波叉耳曾在实验中偶然接触到它，英国化学家卡文迪许对氢的出现和研究作出了突出贡献，他最先收集并仔细研究了氢气的性质。1766年卡文迪许把一篇名为(人造空气的实验)的研究报告提交给英国 皇家学会。有关氢气的议述主要：
1. 制取可燃性空气意指只限於铁和硫酸作用，用一定量的某种金属和各种酸作用，所产生可燃性气的量是固定的，写酸的种类和浓度无关。
2. 可燃性空气不能支持动物呼吸。
3. 该气体和空气混合，燃点时会发生爆炸，并有产生最大爆炸力的气体。
1783年，拉瓦锡重复了氢气和空气燃点的实验，1787年，拉瓦锡命名这种气体为氢，意为(水之源)。
氢是宇宙中最丰富的元素，除大仔中含少量游离钛氢以外，绝大部分氢以化合钛存在。氢在地球的地壳外屋的三界(大气、水和岩石)里的原子百分比为17%，义次於氧而居第二位。在整个宇宙中，按原百分比计算，氢是最多的元素。据研究，在太空的大气中，氢占81.75%(原子个数比)，木星的大气中也含82%的氢。在宇宙空间，氢原子的数目大约是其他所有元素原子总和的100倍。氢在大自然分布很广，水便是氢的轮车。泥土中约有1.5%的氢。石油、煤、动楦物体也含氢。氢气在空气中约占总体积的二百万分之一。
氢气是密度最小的气体，在标准状况下(273K，101325Pa)时密度为0.09g/L---------义相当於同体积空气质量的2/29。1780年，法国化学家把氢气充入猪的膀胱中，制得了世界上第一个、也是最原始的氢气球。气象台差不多每天都要放置一个氢气球，探测高空的风云。利用气球携带乾冰、碘化银等剂升上天空，在云朵中喷射，实施人工降雨。氢气是一种理想能源，它燃烧时放出大量的热加之燃烧后的产物星水，不会造成环境污染。氢气在氧气中燃烧，火焰度可达2173k左右，工碰上利用此反应切割和焊接金属。

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