THIN FILM TRANSISTORS

DEFINITION OF TERM “TFT”A transistor whose active, current-carrying layer is a

thin film (usually a film of silicon), in contrast to MOSFETs, which are made on Si wafers and use the bulk-silicon as the active layer. In a flat-panel display, light must be able to pass through the substrate material to reach the viewer. Opaque silicon wafers obviously will not be suitable for these transmissive displays. Glass is the most commonly used starting substrate because it is highly transparent and is compatible with conventional semiconductor processing steps. Since glass is not a semiconductor like silicon, a thin film of silicon is deposited on top and the transistors are fabricated using this thin layer. Hence, the name "thin-film transistor."

TFT monitor uses thin-film transistor technology for the ultimate LCD display. LCD monitors, also called flat panel displays, are replacing the old style cathode ray tubes (CRTs) as the displays of choice. Nearly all LCD monitors today use TFT technology.

The benefit of a TFT monitor is a separate, tiny transistor for each pixel on the display. Because each transistor is so small, the amount of charge needed to control it is also small. This allows for very fast re-drawing of the display, as the image is re-painted or refreshed several times per second.

THIN FILM TRANSISTOR

TFT MONITORSA TFT monitor delivers crisp text, vibrant

color and an improved response time for multimedia applications. If interested in gaming, video editing or other multimedia applications, look for a TFT monitor with a response rate of 16ms or less.

A typical 17-inch TFT monitor has about 1.3 million pixels and 1.3 million transistors.

ADVANTAGESA dead pixel is a pixel whose transistor has

failed, thereby creating no display image. On a solid black background, dead pixels will stand out as tiny dots of red, white or blue. Most manufacturers will not replace a TFT monitor that has less than 11 dead pixels. Often, a TFT monitor won't have any dead pixels —- always the hope for any buyer, though dead pixels are not noticeable unless located in a critical position on the screen.

APPLICATIONSThe best known application of thin-film

transistors is in TFT LCDs, a variant of LCD technology. Transistors are embedded within the panel itself, reducing crosstalk between pixels and improving image stability.

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.

BYM.K.RAJASEKAR