19-03-2013, 04:54 PM
please explain me about transparent electronics.
19-03-2013, 04:54 PM
please explain me about transparent electronics.
20-03-2013, 10:09 AM
To get full information or details of transparent electronics technology please have a look on the pages
https://seminarproject.net/Thread-transp...ull-report https://seminarproject.net/Thread-transp...s-abstract https://seminarproject.net/Thread-transp...lectronics https://seminarproject.net/Thread-transp...ronics-ppt if you again feel trouble on transparent electronics technology please reply in that page and ask specific fields in transparent electronics technology
13-05-2013, 03:32 PM
TRANSPARENT ELECTRONICS
TRANSPARENT.docx (Size: 26.38 KB / Downloads: 29) ABSTRACT Transparent electronics is an emerging science and technology field focused on producing ‘invisible’ electronic circuitry and opto-electronic devices. Applications include consumer electronics, new energy sources, and transportation; for example, automobile windshields could transmit visual information to the driver. Glass in almost any setting could also double as an electronic device, possibly improving security systems or offering transparent displays. In a similar vein, windows could be used to produce electrical power. Other civilian and military applications in this research field include real time wearable displays. As for conventional Si/III–V-based electronics, the basic device structure is based on semiconductor junctions and transistors. However, the device building block materials, the semiconductor, the electric contacts, and the dielectric/ passivation layers, must now be transparent in the visible –a true challenge! Therefore, the first scientific goal of this technology must be to discover, understand, and implement transparent high-performance electronic materials. The second goal is their implementation and evaluation in transistor and circuit structures. The third goal relates to achieving application-specific properties since transistor performance and materials property requirements vary, depending on the final product device specifications. Consequently, to enable this revolutionary technology requires bringing together expertise from various pure and applied sciences, including materials science, chemistry, physics, electrical/electronic/circuit engineering, and display science. INTRODUCTION Transparent electronics is an emerging science and technology field focused on producing ‘invisible’ electronic circuitry and opto-electronic devices. Applications include consumer electronics, new energy sources, and transportation; for example, automobile windshields could transmit visual information to the driver. Glass in almost any setting could also double as an electronic device, possibly improving security systems or offering transparent displays. In a similar vein, windows could be used to produce electrical power. Other civilian and military applications in this research field include real-time wearable displays. As for conventional Si/III–V-based electronics, the basic device structure is based on semiconductor junctions and transistors. However, the device building block materials, the semiconductor, the electric contacts, and the dielectric/passivation layers, must now be transparent in the visible –a true challenge! Therefore, the first scientific goal of this technology must be to discover, understand, and implement transparent high-performance electronic materials. The second goal is their implementation and evaluation in transistor and circuit structures. The third goal relates to achieving application-specific properties since transistor performance and materials property requirements vary, depending on the final product device specifications. Consequently, to enable this revolutionary technology requires bringing together expertise from various pure and applied sciences, including materials science, chemistry, physics, electrical /electronic/ circuit engineering, and display science. COMBINING OPTICAL TRANSPARENCY WITH ELECTRICAL CONDUCTIVITY Transparent conductors are neither 100% optically transparent nor metallically conductive. From the band structure point of view, the combination of the two properties in the same material is contradictory: a transparent material is an insulator which possesses completely filled valence and empty conduction bands; whereas metallic conductivity appears when the Fermi level lies within a band with a large density of states to provide high carrier concentration. Efficient transparent conductors find their position in a compromise between a sufficient transmission within the visible spectral range and a moderate but useful in practice electrical conductivity. This combination is achieved in several commonly used oxides – In2O3, SnO2, ZnO and CdO. In the undoped stoichiometric state, these materials are insulators with optical band gap of about 3eV. To become a transparent conducting oxide (TCO), these TCO hosts must be degenerately doped to displace the Fermi level up into the conduction band TRANSPARENT ELECTRONICS DEVICES In order to produce a transparent-electronics-based system, appropriate materials must be selected, synthesized, processed, and integrated together in order to fabricate a variety of different types of devices. In turn, these devices must be chosen, designed, fabricated, and interconnected in order to construct circuits, each of which has to be designed, simulated, and built in such a way that they appropriately function when combined together with other circuit and ancillary non-circuit subsystems. Thus, this product flow path involves materials→ devices → circuits → systems, with each level of the flow more than likely involving multi-feedback iterations of selection, design, simulation, fabrication, integration, characterization, and optimization. From this perspective, devices constitute a second level of the product flow path. The multiplicity, performance, cost, manufacturability, and reliability of available device types will dictate the commercial product space in which transparent electronics technology will be able to compete. Thus, an assessment of the device toolset available to transparent electronics is of fundamental interest, and is the central theme of this chapter. Passive, linear devices - resistors, capacitors, and inductors – comprise the first topic discussed. Passive devices are usually not perceived to be as glamorous as active devices, but they can be enabling from a circuit system perspective, and they are also the simplest device types from an operational point-of-view. Together, these two factors provide the rationale for considering this topic initially .Next, two-terminal electronic devices - pn junctions, Schottky barriers, hetero junctions, and metal-insulator-semiconductor (MIS) capacitors – constitute the second major topic. The motivation for this topical ordering is again associated with their relative operational complexity, rather than their utility. The third and final major topic addressed is transistors. This is the most important matter considered in this chapter. Most of this discussion focuses on TTFTs, since they are perceived to be the most useful type of transistor for transparent electronics. Additionally, a very brief overview of alternative transistor types -static-induction transistors, vertical TFTs, hot electron transistors, and nano wire transistors - is included. This is motivated by recognizing the desirability of achieving higher operating frequencies than are likely obtainable using TTFT switch minimum gate lengths greater than ~2-10μm, a probable lower-limit dimensional constraint for many types of low-cost, large-area applications. Alternative transistors such as these offer possible routes for reaching higher operating frequencies, in the context of transparent electronics. TRANSPARENT THIN-FILM RESISTORS (TTFR’S) An ideal resistor is a device whose current-voltage characteristics are linear, described by Ohm’s Law, and which dissipates power if a voltage exists across it. A real resistor may not be perfectly linear, i.e., precisely obey Ohm’s Law, and may also possess some undesirable capacitive or inductive parasitic characteristics. Transparent thin-film resistors (TTFRs) are expected to operate at relatively low frequencies, so that parasitic inductance is not anticipated to be relevant. Additionally, TTFRs will most likely be fabricated on insulating substrates, so that parasitic capacitance should be minimal. Finally, if properly designed, a TTFR is expected to exhibit linear or very near-linear behavior. Thus, in most respects, we expect a TTFR to be adequately modeled as an ideal resistor .TTFR resistance tolerance is expected to be similar to that of conventional thin film resistors, ±10%, unless resistor trimming is performed, in which case a tolerance of approximately ±0.1% is possible. It is not clear whether resistor trimming will be practical in a transparent electronics technology, given its anticipated low-cost structure. Smooth surfaces are highly desirable for TTFR applications, suggesting that amorphous layers would be preferred. TRANSPARENT THIN-FILM CAPACITORS (TTFC’s) An ideal capacitor is an electric field energy storage device possessing linear current-voltage derivative (idv/dt) characteristics. Usually a large capacitance density is desired, in order to minimize the size of a capacitor. Therefore, a thin insulator with a high dielectric constant (sometimes referred to as a ‘high-k dielectric’ ,where ‘k’ denotes the relative dielectric constant) is best. However, a high-k dielectric typically has a smaller band gap , which usually results in a low breakdown electric field. Although reducing the insulator thickness also increases the capacitance density, a minimum thickness is required to avoid pinholes and other types of defects which degrade the breakdown field and which yield more insulator leakage. Although TTFC performance may be degraded by inductive and resistive parasitic effects, neither of these are expected to be severe given that these devices are expected to be used at relatively low frequencies and that low leakage thin-film insulators are already employed in non-transparent applications. From process integration, manufacturability, and reliability considerations, TTFC contacts and insulators should ideally be amorphous. TRANSPARENT THIN-FILM INDUCTORS (TTFI’S) An ideal inductor is a magnetic field energy storage device possessing linear voltage-current derivative (vdi/dt) characteristics. In contrast to a TTFR and a TTFC, transparent thin-film inductor (TTFI) and related transparent magnetically-coupled devices are expected to behave in anon-ideal manner. Two main reasons underlie this expectation. First, because of the relatively poor conductance of TCOs compared to metals, TTFIs will possess a significant amount of parasitic resistance. Second, efficient magnetic field coupling is strongly facilitated by the use of a magnetically-permeable insulator. However, we are not aware of a transparent, magnetically-permeable insulator material. Thus, realizing high performance TTFIs and related magnetically coupled devices is expected to be a challenging task. The quality factor, Q, is basically an inductor performance figure-of-merit. A larger Q is better. Thus, since the parasitic resistance of a TTFI is expected to be large, as a consequence of employing a TCO instead of a metal, high-Q TTFI’s are not expected. However, needing to have a large number of turns is likely to cause trouble, since having a large number of turns will increase the inductor parasitic series resistance, and probably also the inductor parasitic capacitance. These TTFI challenges are disappointing since a TTFI and its magnetically coupled device variants are potentially application-enabling, performance enhancing components. Inductors are useful in resonant circuits and filters. They can also function as power supply chokes (limiting current fluctuations), energy storage devices for switched-mode power supplies, etc. Furthermore, magnetically-coupled inductors may be used for the construction of transformers for power and signal conditioning. Finally, a somewhat-related application is that of an antenna to transmit or receive RF signals. In this regard, we note that a transparent microwave antenna constructed using ITO has been reported. Even though a TTFI with good performance appears to be difficult to construct, the benefits of magnetic field coupling devices appear to offer enough enticements to warrant further investigation. |
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