We explore the interrelationships between the green 510 nm emission, the free‐carrier concentration, and the paramagnetic oxygen‐vacancy density in commercial ZnO phosphors by combining photoluminescence, optical‐absorption, and electron‐paramagnetic‐resonance spectroscopies. We find that the green emission intensity is strongly influenced by free‐carrier depletion at the particle surface, particularly for small particles and/or low doping. Our data suggest that the singly ionized oxygen vacancy is responsible for the green emission in ZnO; this emission results from the recombination of a photogenerated hole with the singly ionized charge state of this defect.

Mechanisms behind green photoluminescence in ZnO phosphor powders

Transparent electronics is today one of the most advanced topics for a wide range of device applications. The key components are wide bandgap semiconductors, where oxides of different origins play an important role, not only as passive component but also as active component, similar to what is observed in conventional semiconductors like silicon. Transparent electronics has gained special attention during the last few years and is today established as one of the most promising technologies for leading the next generation of flat panel display due to its excellent electronic performance. In this paper the recent progress in n- and p-type oxide based thin-film transistors (TFT) is reviewed, with special emphasis on solution-processed and p-type, and the major milestones already achieved with this emerging and very promising technology are summarizeed. After a short introduction where the main advantages of these semiconductors are presented, as well as the industry expectations, the beautiful history of TFTs is revisited, including the main landmarks in the last 80 years, finishing by referring to some papers that have played an important role in shaping transparent electronics. Then, an overview is presented of state of the art n-type TFTs processed by physical vapour deposition methods, and finally one of the most exciting, promising, and low cost but powerful technologies is discussed: solution-processed oxide TFTs. Moreover, a more detailed focus analysis will be given concerning p-type oxide TFTs, mainly centred on two of the most promising semiconductor candidates: copper oxide and tin oxide. The most recent data related to the production of complementary metal oxide semiconductor (CMOS) devices based on n- and p-type oxide TFT is also be presented. The last topic of this review is devoted to some emerging applications, finalizing with the main conclusions. Related work that originated at CENIMAT|I3N during the last six years is included in more detail, which has led to the fabrication of high performance n- and p-type oxide transistors as well as the fabrication of CMOS devices with and on paper.

Oxide Semiconductor Thin‐Film Transistors: A Review of Recent Advances

Solar cells based on organometallic halide perovskite absorber layers are emerging as a high-performance photovoltaic technology. Using highly sensitive photothermal deflection and photocurrent spectroscopy, we measure the absorption spectrum of CH3NH3PbI3 perovskite thin films at room temperature. We find a high absorption coefficient with particularly sharp onset. Below the bandgap, the absorption is exponential over more than four decades with an Urbach energy as small as 15 meV, which suggests a well-ordered microstructure. No deep states are found down to the detection limit of ∼1 cm–1. These results confirm the excellent electronic properties of perovskite thin films, enabling the very high open-circuit voltages reported for perovskite solar cells. Following intentional moisture ingress, we find that the absorption at photon energies below 2.4 eV is strongly reduced, pointing to a compositional change of the material.

Organometallic Halide Perovskites: Sharp Optical Absorption Edge and Its Relation to Photovoltaic Performance

Numerous candidates attempting to replace Si-based flash memory have failed for a variety of reasons over the years. Oxide-based resistance memory and the related memristor have succeeded in surpassing the specifications for a number of device requirements. However, a material or device structure that satisfies high-density, switching-speed, endurance, retention and most importantly power-consumption criteria has yet to be announced. In this work we demonstrate a TaO(x)-based asymmetric passive switching device with which we were able to localize resistance switching and satisfy all aforementioned requirements. In particular, the reduction of switching current drastically reduces power consumption and results in extreme cycling endurances of over 10(12). Along with the 10 ns switching times, this allows for possible applications to the working-memory space as well. Furthermore, by combining two such devices each with an intrinsic Schottky barrier we eliminate any need for a discrete transistor or diode in solving issues of stray leakage current paths in high-density crossbar arrays.

A fast, high-endurance and scalable non-volatile memory device made from asymmetric Ta2O5−x/TaO2−x bilayer structures

Graphene has been hailed as a wonderful material in electronics, and recently, it is the rising star in photonics, as well. The wonderful optical properties of graphene afford multiple functions of signal emitting, transmitting, modulating, and detection to be realized in one material. In this paper, the latest progress in graphene photonics, plasmonics, and broadband optoelectronic devices is reviewed. Particular emphasis is placed on the ability to integrate graphene photonics onto the silicon platform to afford broadband operation in light routing and amplification, which involves components like polarizer, modulator, and photodetector. Other functions like saturable absorber and optical limiter are also reviewed.

Graphene photonics, plasmonics, and broadband optoelectronic devices.

Author(s): Brovn, David; Gidal, George; Birge, Robert W.; Bacastov, Robert; Fung, Sun Yiu; Jackson, Warren; Pu, Robert.

https://escholarship.org/content/qt9vx164kj/qt9vx164kj.pdf?t=p0jun5

QUASI-TWO-BODY FINAL STATES PRODUCED IN $pi$$sup +$p INTERACTIONS BETWEEN 3 AND 4 GeV/c.

Paper transport subsystems transport sheets of paper from a starting point to a final destination with high accuracy and reliability. Traditional roller-based transport systems consist of rollers operating in an open loop mode. Therefore, such systems do not exhibit graceful degradation and adaptable control. We present a distributed hybrid hierarchical control for transport systems which are flexible, modular, and exhibit graceful degradation of throughput.

A hybrid hierarchical control architecture for paper transport systems

Large Area Flexible Electronics Fabricated Using Self-Aligned Imprint Lithography

The electronic stability of a-Si:H deposited in a remote hydrogen plasma reactor at high temperatures (e.g., T D =400 o C) and hydrogen dilution (e.g., H 2 to SiH 4 ratio of 20:1) is significantly different from that of optimized electronic-grade films from rf glow discharge deposition. This is a previously unexplored «parameter space» that should be accessible to other deposition techniques

Stability of a-Si:H deposited at high temperatures and hydrogen dilution in a remote hydrogen plasma reactor

Continuous constrained optimization is at the core of many real-world applications such as planning, scheduling, control, and diagnosis of physical systems (car, planes, factories). Effective constraintbased techniques must handle the complexity of real-world continuous constraint problems by dynamically adapting solvers to the structure of the problem. Toward this end, we analyze continuous constraint satisfaction problem formulations based on (discrete) 3-SAT problems, which have a strong relation between structure and search cost. We compare the search complexities of three different problem formulations and three randomized search algorithms. This allows us not only to compare different problems and solution approaches, but also to connect back to results from similar studies on SAT problems. In particular, we find that median search cost is characterized by simple parameters such as the constraint-to-variable ratio, and that discrete search algorithms such as GSAT have continuous counter-parts with similar behavior.

Warren B. Jackson

Papers

QUASI-TWO-BODY FINAL STATES PRODUCED IN $pi$$sup +$p INTERACTIONS BETWEEN 3 AND 4 GeV/c.

A hybrid hierarchical control architecture for paper transport systems

Large Area Flexible Electronics Fabricated Using Self-Aligned Imprint Lithography

Stability of a-Si:H deposited at high temperatures and hydrogen dilution in a remote hydrogen plasma reactor

Complexity of Continuous, 3-SAT-like Constraint Satisfaction Problems