Thin film diode (TFD) generally refers to any
diode
A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other.
A diode ...
produced using
thin-film
A thin film is a layer of material ranging from fractions of a nanometer (monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films (a process referred to as deposition) is a fundamental step in many ap ...
technology.
Within the
flat panel display
A flat-panel display (FPD) is an electronic display used to display visual content such as text or images. It is present in consumer, medical, transportation, and industrial equipment.
Flat-panel displays are thin, lightweight, provide better li ...
industry TFD more often refers to thin film bi-directional diodes, also known as metal-insulator-metal (MIM) TFDs or nonlinear resistors. Bi-directional MIM TFDs have very low
current
Currents, Current or The Current may refer to:
Science and technology
* Current (fluid), the flow of a liquid or a gas
** Air current, a flow of air
** Ocean current, a current in the ocean
*** Rip current, a kind of water current
** Current (stre ...
flow at low applied
voltages
Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to mo ...
, but then begin to conduct electricity above a threshold voltage, of either positive or negative polarity. Owing to this behavior these two terminal devices may be used as a switch. The exact threshold voltage at which a MIM TFD switches on and begins to conduct electricity depends on its physical dimensions, such as thickness of the insulating layer, as well as the physical properties of the materials from which it is made, such as the
work function
In solid-state physics, the work function (sometimes spelt workfunction) is the minimum thermodynamic work (i.e., energy) needed to remove an electron from a solid to a point in the vacuum immediately outside the solid surface. Here "immediately" m ...
of each metal layer.
Commercial applications
Flat panel display manufactures have found use for MIM TFDs as switches in
active matrix Active matrix is a type of addressing scheme used in flat panel displays. In this method of switching individual elements (pixels), each pixel is attached to a transistor and capacitor ''actively'' maintaining the pixel state while other pixels ar ...
technology such as
active matrix liquid crystal displays (AMLCD). Historically in AMLCDs the switching device of choice for pixels has been the
thin-film transistor
A thin-film transistor (TFT) is a special type of field-effect transistor (FET) where the transistor is thin relative to the plane of the device. TFTs are grown on a supporting (but non-conducting) substrate. A common substrate is glass, becaus ...
(TFT), however MIM TFD based displays have had some commercial success as they are simpler to make; only requiring two to three
photo-lithography
In integrated circuit manufacturing, photolithography or optical lithography is a general term used for techniques that use light to produce minutely patterned thin films of suitable materials over a substrate, such as a silicon wafer, to protec ...
steps rather than the typical 5 or more needed to produce thin film transistors.
In short, the millions of switches housed on an active matrix display's back-plane, be they TFTs or TFDs, must each be able to accurately and repeatably control the voltage applied to their respective pixel in order to control its grey scale. While thin film diodes are cheaper to manufacture than TFTs it can difficult to achieve a wide color gamut and grey scale using single TFDs. These limitation can be overcome however by using a dual-select diode circuit which incorporates two MIM TFDs per pixel circuit.
South Korean electronics manufacturers
LG and
Samsung
The Samsung Group (or simply Samsung) ( ko, 삼성 ) is a South Korean multinational manufacturing conglomerate headquartered in Samsung Town, Seoul, South Korea. It comprises numerous affiliated businesses, most of them united under the ...
have both previously incorporated MIM TFDs into mobile phone displays. The American company Amorphyx Inc. was founded in 2012 to commercialize MIM-TFD technology incorporating amorphous metal materials.
[Amorphyx Inc. website, accessed 9/12/12, http://www.amorphyx.com]
See also
*
Active-matrix liquid crystal display
An active-matrix liquid-crystal display (AMLCD) is a type of flat-panel display, the only viable technology for high-resolution TVs, computer monitors, notebook computers, tablet computers and smartphones with an LCD screen, due to low weight, ...
*
Liquid crystal display television
Liquid-crystal-display televisions (LCD TVs) are television sets that use liquid-crystal displays to produce images. They are, by far, the most widely produced and sold television display type. LCD TVs are thin and light, but have some disadvantag ...
References
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External links
Varieties & Qualities Of Diodes
Diodes