A thin film transistor (TFT) is a special kind of field effect transistor made by depositing thin films of a semiconductor active layer as well as the dielectric layer and metallic contacts over a supporting substrate. The field-effect transistor (FET is a type of Transistor that relies on an Electric field to control the shape and hence the conductivity of a 'channel' Thin films are thin material layers ranging from fractions of a Nanometre to several Micrometres in thickness A semiconductor' is a Solid material that has Electrical conductivity in between a conductor and an insulator; it can vary over that A dielectric is a nonconducting substance ie an insulator. The term was coined by William Whewell in response to a request from Michael Faraday. A common substrate is glass, since the primary application of TFTs is in liquid crystal displays. Glass in the common sense refers to a Hard, Brittle, transparent Solid, such as that used for Windows many This differs from the conventional transistor where the semiconductor material typically is the substrate, such as a silicon wafer. In Electronics, a transistor is a Semiconductor device commonly used to amplify or switch electronic signals A wafer is a thin slice of Semiconductor material such as a Silicon crystal used in the fabrication of Integrated circuit and other microdevices

TFTs can be made using a wide variety of semiconductor materials. A common material is silicon. Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 The characteristics of a silicon based TFT depend on the crystalline state. That is, the semiconductor layer can be either amorphous silicon,^[1] microcrystalline silicon,^[1] or it can be annealed into polysilicon. Amorphous silicon (a-Si is the non-crystalline Allotropic form of Silicon. Nanocrystalline silicon ( nc-Si)—an allotropic form of Silicon with Paracrystalline structure—is similar to Amorphous silicon Other materials which have been used as semiconductors in TFTs include compound semiconductors such as cadmium selenium (CdSe)^[2][3] and metal oxides such as Zinc Oxide. ^[4] TFT's have also been made using organic materials (referred to as an Organic TFT or OTFT). An Organic Field-Effect Transistor (OFET is a Field effect transistor using an Organic semiconductor in its channel

By using transparent semiconductors and transparent electrodes, such as indium tin oxide (ITO), some TFT devices can be made completely transparent. Uses ITO is mainly used to make transparent conductive coatings for Liquid crystal displays Flat panel displays Plasma displays touch panels

Because the substrate cannot withstand the high annealing temperature, the deposition process has to be completed under relatively low temperature. Chemical vapor deposition, physical vapor deposition (usually sputtering) are applied. Chemical vapor deposition (CVD is a Chemical process used to produce high-purity high-performance solid materials Physical vapor deposition (PVD is a variety of vacuum deposition and is a general term used to describe any of a variety of methods to deposit Thin films by the condensation Sputtering is a process whereby Atoms are Ejected from a solid target material due to bombardment of the target by energetic Ions It is commonly used for Also the first solution processed transparent TFTs (TTFTs), based on zinc oxide were reported in 2003 by researchers at Oregon State University. Zinc oxide is a Chemical compound with the formula ZnO It is nearly insoluble in water but soluble in Acids and Bases It occurs Year 2003 ( MMIII) was a Common year starting on Wednesday of the Gregorian calendar. Oregon State University ( OSU) is a Coeducational public Research[[ university]] located in Corvallis, Oregon, United ^[4]

Applications

The best known application of thin-film transistors is in TFT LCDs, a variant of LCD technology. A thin film transistor liquid crystal display ( TFT-LCD) is a variant of Liquid crystal display (LCD which uses Thin film transistor (TFT technology to Transistors are embedded within the panel itself, reducing crosstalk between pixels and improving image stability. In Digital imaging, a pixel ( pict ure el ement is the smallest piece of information in an image As of 2004, all but the cheapest color LCD screens use this technology. "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " TFT panels are heavily used in digital radiography applications in General Radiography. It is used in both Direct and Indirect capture as a base for the Image Receptor in Radiography.

The new AMOLED (Active Matrix OLED) screens also contain a TFT layer. An active matrix Liquid crystal display ( AMLCD) is a type of Flat panel display, currently the overwhelming choice of Notebook computer An Organic Light Emitting Diode ( OLED) also Light Emitting Polymer ( LEP) and Organic Electro Luminescence ( OEL) is any

See also

• Liquid crystal display television
• Organic Thin Film Transistors

References

1. ^ ^{a b} Kanicki, Jerzy (1992). Liquid-crystal display televisions ( LCD TV) are Television sets that use LCD technology to produce images An Organic Field-Effect Transistor (OFET is a Field effect transistor using an Organic semiconductor in its channel Amorphous & Microcystalline Semiconductor Devices Volume II: Materials and Device Physics. Artech House, Inc. . ISBN 0-89006-379-6.  
2. ^ Brody, T. Peter (November 1984). "The Thin Film Transistor - A Late Flowering Bloom". IEEE Transactions on Electron Devices 31 (11): 1614-1628.  
3. ^ Brody, T. Peter (1996). "The birth and early childhood of active matrix - a personal memoir". Jounal of the SID 4/3: 113-127.  
4. ^ ^{a b} Wager, John. OSU Engineers Create World's First Transparent Transistor. College of Engineering, Oregon State University, Corvallis, OR: OSU News & Communication, 2003. 29 July 2007.