Amorphous silicon

About: Amorphous silicon is a research topic. Over the lifetime, 26777 publications have been published within this topic receiving 423234 citations.

Substrate conformal imprint lithography for nanophotonics

Abstract: The field of nano-photonics studies the interaction and control of light with dielectric, semiconductor and metal structures which are comparable in size or smaller than the vacuum wavelength of light. In this thesis we present Substrate Conformal Imprint Lithography (SCIL) as a novel wafer-scale nanoimprint method with nano-scale resolution which combines the resolution and accuracy of rigid stamps with the flexibility of soft stamp methods. Chapter two describes the SCIL soft nanoimprint process and introduces a novel silica sol-gel imprint resist. A new soft rubber stamp material is described which enables sub-10 nm resolution. We demonstrate that SCIL imprinted patterns have on average less than 0.1 nm distortion and demonstrate sub–50 nm overlay alignment. Chapter 3 demonstrates 30 nm dense structures and features with aspect ratios from 1/640 up to 5. Imprinted sol-gel patterns can be transferred into underlying materials while maintaining sub-10 nm resolution. Two methods are demonstrated to pattern noble metals in particle arrays and sub-wavelength hole arrays. SCIL is applied to produce photonic crystal power InGaN LEDs which exhibit strong modification of the emission pattern. Chapter 4 demonstrates a relatively simple route towards 3D woodpile type photonic crystals. We show a four layer woodpile type structure with 70 nm features on a 240 nm pitch, which is temperature stable up to 1000 C. Chapter 5 demonstrates a novel fabrication route to large area nano hole arrays, which are interesting as angle independent color filters and for sensor applications. A solid state index matched hole array exhibits SPP mediated super resonant transmission. Chapter 6 treats single mode polarization stabilized Vertical Cavity Surface Emitting Lasers (VCSELs). The lasers produced by SCIL exhibit equal performance as devices produced by e-beam. VCSELs with SCIL imprinted sub-wavelength gratings increase the laser efficiency by 29 % compared to conventional gratings. Chapter 7 studies the improved red light absorption in thin film hydrogenated amorphous silicon (a-Si:H) solar cells with plasmonic back mirrors. Thin film a-Si:H solar cells are made on SCIL structured silver mirrors and smooth reference silver mirrors. Patterning increases the external collection efficiency to 6.2 %, an increase of 26 % compared to smooth reference cells. This increase is due to an enhanced absorption in the 600-800 nm wavelength range. Chapter 8 studies the performance of ultra thin silicon solar cells. We use SCIL to pattern substrates which a large variety of nano patterns on which thin film a-Si:H solar cells are processed with a thickness of 160 and 340 nm. A 160 nm thick silicon cell is also made on randomly textured glass. The best patterned cells with 160 nm thick silicon exhibit an external collection efficiency of 6.6 %, equal to that of the best thicker cells and 37.8% better than flat cells. Crucially, some regular patterns exhibited improved efficiency over cells made on randomly textured glass, which we attribute to coupling of non-absorbed light to waveguide modes in the silicon.

Electrophotographic patterning of thin film circuits

Abstract: Amorphous silicon thin-film transistors on glass foil are made using exclusively electrophotographic printing for pattern formation, contact hole opening, and device isolation. Toner etch masks are applied by feeding the glass substrate through a laser printer or photocopier, or from laser-printed patterns on transfer paper. This all-printed patterning is a low-cost, large-area circuit processing technology, suitable for producing backplanes for active matrix liquid crystal displays.

Kinetics of the Staebler–Wronski effect in hydrogenated amorphous silicon

Abstract: We have investigated the time and intensity dependence of the creation process for light‐induced metastable defects (Staebler–Wronski effect) in hydrogenated amorphous silicon (a‐Si:H). The observed changes in electron spin resonance spin density (dangling bonds) and photoconductivity are consistent with a model which explains the Staebler–Wronski effect as a self‐limiting process intrinsic to a‐Si:H. A possible microscopic mechanism based on the nonradiative recombination of band tail carriers is discussed.

Protective overlayer material and electro-optical coating using same

Abstract: An electro-optical device comprising a series of thin films with an electrically controllable optical state provided with a protective overlayer that has a high optical transmittance and high resistance to penetration by H2 O. The protective overlayer is a film of amorphous silicon oxycarbide (a-SiOC:H) having an O to C ratio such that the optical absorption edge of the a-SiOC:H is 3 eV or greater and the H2 O transport through a 500 nm thick film of a-SiOC:H is 1012 molecules/cm2 -s or less.