Thin film diode (TFD) generally refers to any
diode
A diode is a two-Terminal (electronics), terminal electronic component that conducts electric current primarily in One-way traffic, one direction (asymmetric electrical conductance, conductance). It has low (ideally zero) Electrical resistance ...
produced using
thin-film
A thin film is a layer of materials 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 a ...
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 ...
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 (hydr ...
flow at low applied
voltages
Voltage, also known as (electrical) potential difference, electric pressure, or electric tension, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge t ...
, 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 spelled 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" ...
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. It is a method of switching individual elements of a flat panel display, known as pixels. Each pixel is attached to a transistor and capacitor that ''actively'' maintain th ...
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 made by thin film deposition. TFTs are grown on a supporting (but non-conducting) substrate, such as glass. This differs from the convention ...
(TFT), however MIM TFD based displays have had some commercial success as they are simpler to make; only requiring two to three
photo-lithography
Photolithography (also known as optical lithography) is a process used in the manufacturing of integrated circuits. It involves using light to transfer a pattern onto a substrate, typically a silicon wafer.
The process begins with a photosensiti ...
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
Samsung Group (; stylised as SΛMSUNG) is a South Korean Multinational corporation, multinational manufacturing Conglomerate (company), conglomerate headquartered in the Samsung Town office complex in Seoul. The group consists of numerous a ...
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 an extremely common type of liquid-crystal display (LCD). Having supplanted passive-matrix LCDs in general use, in common vernacular, an active-matrix LCD is also simply referred to as a LCD. As ...
*
LCD television
A liquid-crystal-display television (LCD TV) is a television set that uses a liquid-crystal display to produce images. It is by far the most widely produced and sold type of television display. LCD TVs are thin and light, but have some disadvanta ...
References
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External links
Varieties & Qualities Of Diodes
Diodes