SEMICONDUCTORS THE SILICON CHIP Silicon Is The Raw Material Most Oft

SEMICONDUCTORS : THE SILICON CHIP Silicon is the raw material most often used in integrated circuit (IC) fabrication. It is the second most abundant substance on the earth. It is extracted from rocks and common beach sand and put through an exhaustive purification process. In this form, silicon is the purist industrial substance that man produces, with impurities comprising less than one part in a billion. That is the equivalent of one tennis ball in a string of golf balls stretching from the earth to the moon. Semiconductors are usually materials which have energy-band gaps smaller than 2eV. An important property of semiconductors is the ability to change their resistivity over several orders of magnitude by doping. Semiconductors have electrical resistivities between 10-5 and 107 ohms. Semiconductors can be crystalline or amorphous. Elemental semiconductors are simple-element semiconductor materials such as silicon or germanium. Silicon is the most common semiconductor mat erial used today. It is used for diodes, transistors, integrated circuits, memories, infrared detection and lenses, light-emitting diodes (LED), photosensors, strain gages, solar cells, charge transfer devices, radiation detectors and a variety of other devices. Silicon belongs to the group IV in the periodic table. It is a grey brittle material with a diamond cubic structure. Silicon is conventionally doped with Phosphorus, Arsenic and Antimony and Boron, Aluminum, and Gallium acceptors. The energy gap of silicon is 1.1 eV. This value permits the operation of silicon semiconductors devices at higher temperatures than germanium. Now I will give you some brief history of the evolution of electronics which will help you understand more about semiconductors and the silicon chip. In the early 1900's before integrated circuits and silicon chips were invented, computers and radios were made with vacuum tubes. The vacuum tube was invented in 1906 by Dr.Lee DeForest. Throughout the first half of the 20th century, vacuum tubes were used to conduct, modulate and amplify electrical signals. They made possible a variety of new products including the radio and the computer. However vacuum tubes had some inherent problems. They were bulky, delicate and expensive, consumed a great deal of power, took time to warm up, got very hot, and eventually burned out. The first digital computer contained 18,000 vacuum tubes, weighed 50 tins, and required 140 kilowatts of power. By the 1930's, researchers at the Bell Telephone Laboratories were looking for a replacement for the vacuum tube. They began studying the electrical properties of semiconductors which are non-metallic substances, such as silicon, that are neither conductors of electricity, like metal, nor insulators like wood, but whose electrical properties lie between these extremes. By 1947 the transistor was invented. The Bell Labs research team sought a way of directly altering the electrical properties of semiconducto r material. They learned they could change and control these properties by "doping" the semiconductor, or infusing it with selected elements, heated to a gaseous phase. When the semiconductor was also heated, atoms from the gases would seep into it and modify its pure, crystal structure by displacing some atoms. Because these dopant atoms had different amount of electrons than the semiconductor atoms, they formed conductive paths. If the dopant atoms had more electrons than the semiconductor atoms, the doped regions were called n-type to signify and excess of negative charge. Less electrons, or an excess of positive charge, created p-type regions. By allowing this dopant to take place in carefully delineated areas on the surface of the semiconductor, p-type regions could be created within n-type regions, and vice-versa. The transistor was much smaller than the vacuum tube, did not get very hot, and did not require a headed filament that would eventually burn out. Finally in 1958, integrated circuits were invented. By the mid 1950's, the first commercial transistors were being shipped. However research continued. The scientist began to think that if one transistor could be built within one solid piece of semiconductor material, why not multiple transistors or even an entire circuit. With in a few years this speculation became one solid piece of material. These integrated circuits(ICs) reduced the number of electrical interconnections required in a piece of electronic equipment, thus increasing reliability and speed. In contrast, the first digital electronic computer built with 18,000 vacuum

Financial measures for General Electric

Financial measures for General Electric - good jobTo : The Board of Directors, GENERAL ELECTRIC COMPANYSubject : NEW FINANCIAL AND STATISTICAL MEASURES TO MONITORTHE SUCCESS OF GENERAL ELECTRIC COMPANYAfter Mr. Weltch announced my new assignment, I pondered how I could go about guaranteeing the best possible result: a creditable and well organized work that is going to help you, the Board of Directors, plan for the future of the company in a better way. Before starting my analysis, I must specify that my target is not to abolish the traditionally used financial and statistical measures but to develop new ones to be used as guidance for the corporations future development.Our Chairman recently wrote that "the hottest trend in business in 1995 and the one that hit closest to home is the rush toward breaking up multi-business companies and spinning off their components, under the theory that their size and diversity inhibited their competitiveness ...English: Sneinton Cliffs The result of clay quarry...breaking up is the ri ght answer for some big companies ... for us it is the wrong answer."1For us the new trend is the entrance into the service industry.The question must then be: is this the right answer?GE is expecting to increase its revenue by the year 2000 to $120 billion compared with $58 billion in 1990. In other words, if the forecast proves to be correct, it will obtain an average annual rate of growth of 7.5%. This high rate is mainly attributed to the expansion of the services sector of the company, which is estimated to increase by an average annual rate of 13% compared with a corresponding one of 2.1% for manufacturing. Today nearly 60% of GEs profits comes from services up from 16.4% in 1980.2This is our new direction and therefore my target...

Compare and contrast attitudes towards Native Americans Essay

Compare and contrast attitudes towards Native Americans - Essay Example Even though white American treated American Indians in hostile manner, the latter considered the former as brothers. The American Indian was always treated unfairly and was not rewarded for their efforts and they often survived liked invisible Americans. They were given small reservations and were cut off from the rest of the country. Many Americans who live out of the West have no idea that Native Americans did survive in America. Traditionally, Americans neglected Native Americans and did not give any rights or privilege to this community. Americans felt that even though Native Americans had noble qualities, in the end they are evil, treacherous and cruel. Native Americans were a minority and were treated with injustice by white Americans. Americans kept a distance from Native Americans as they were believed to be lazy, uncivilized and vengeful. Native Americans had been neglected throughout the history of America, until the media started focusing on them. It was in 1960 that two books on American Indians throw some light upon their importance and culture. In 1960s Native Americans received more attention among white Americans and this led to greater awareness of American Indians and the troubles they faced in their daily life. The American Indians utilized the publicity they had among white Indians and the Americans started caring more for their needs and desire. Americans started feeling sympathetic towards Native Americans and started realizing their rights and needs. So the media started to focus on their problems, history and explained the pain they suffered at the hands of white Americans. The plight of the Native Americans is poor because they are largely misunderstood by the White Americans. The problem is the both the parties does not attempt to understand each other. It was in late 20th century that the Americans started realizing that America is not