TY - GEN A1 - Käso, Mathias A1 - Wulf, Ulrich A1 - Kucera, Jan A1 - Richter, Hans A1 - Höntschel, Jan T1 - Thermal properties of quantum devices in integrated circuits embedded in a chip environment T2 - Physica Status Solidi C N2 - We consider a thermal model for an integrated circuit including its chip environment. As the simplest choice, the active device layer (integrated circuit) consists of an array of replicas of the same quantum device with the same time depended average temperature. Modeling the chip environment we assume this active layer is sandwiched between two coplanar heat reservoirs. The top heat reservoir represents the wiring layer of the chip (‘back-end of line’). Its temperature is predominantly determined by the dissipated Joule heat in the wiring, typically in the order of one hundred degrees of Celsius. The bottom reservoir represents the cooling unit at about room-temperature. We solve the coupled equations describing thermal transport between the active layer and surrounding heat reservoirs and electrical transport in the quantum devices. The stationary working temperatures of the considered quantum devices can be found from a fix-point problem. A proper linearization of the complete time-depended problem yields the stability of these fixpoints. Numerical solutions for a device layer consisting of identical nano-transistors are given for selected parameters. KW - Thermal properties of quantum devices KW - Transport KW - Chip Y1 - 2014 U6 - https://doi.org/10.1002/pssc.201300203 SN - 1610-1642 N1 - E-MRS 2013 Spring Meeting Symposium VL - 11 IS - 1 SP - 105 EP - 108 ER - TY - GEN A1 - Wulf, Ulrich A1 - Kučera, Jan A1 - Richter, Hans A1 - Horstmann, Manfred A1 - Wiatr, Maciej A1 - Höntschel, Jan T1 - Channel Engineering for Nanotransistors in a Semiempirical Quantum Transport Model T2 - Mathematics N2 - One major concern of channel engineering in nanotransistors is the coupling of the conduction channel to the source/drain contacts. In a number of previous publications, we have developed a semiempirical quantum model in quantitative agreement with three series of experimental transistors. On the basis of this model, an overlap parameter 0≤C≤1 can be defined as a criterion for the quality of the contact-to-channel coupling: A high level of C means good matching between the wave functions in the source/drain and in the conduction channel associated with a low contact-to-channel reflection. We show that a high level of C leads to a high saturation current in the ON-state and a large slope of the transfer characteristic in the OFF-state. Furthermore, relevant for future device miniaturization, we analyze the contribution of the tunneling current to the total drain current. It is seen for a device with a gate length of 26 nm that for all gate voltages, the share of the tunneling current becomes small for small drain voltages. With increasing drain voltage, the contribution of the tunneling current grows considerably showing Fowler–Nordheim oscillations. In the ON-state, the classically allowed current remains dominant for large drain voltages. In the OFF-state, the tunneling current becomes dominant. KW - nanotransistor KW - channel engineering KW - quantum transport KW - contact-to-channel coupling KW - wave function overlap KW - tunneling current Y1 - 2017 UR - http://www.mdpi.com/2227-7390/5/4/68 U6 - https://doi.org/10.3390/math5040068 SN - 2227-7390 VL - 5 IS - 4 ER - TY - GEN A1 - Brinkert, Katharina A1 - Richter, Matthias A1 - Akay, Ömer A1 - Liedtke, Janine A1 - Giersig, Michael A1 - Fountaine, Katherine T. A1 - Lewerenz, Hans-Joachim T1 - Efficient Solar Hydrogen Generation in Microgravity Environment T2 - Nature Communications N2 - Long-term space missions require extra-terrestrial production of storable, renewable energy. Hydrogen is ascribed a crucial role for transportation, electrical power and oxygen generation. We demonstrate in a series of drop tower experiments that efficient direct hydrogen production can be realized photoelectrochemically in microgravity environment, providing an alternative route to existing life support technologies for space travel. The photoelectrochemical cell consists of an integrated catalyst-functionalized semiconductor system that generates hydrogen with current densities >15 mA/cm2 in the absence of buoyancy. Conditions are described adverting the resulting formation of ion transport blocking froth layers on the photoelectrodes. The current limiting factors were overcome by controlling the micro- and nanotopography of the Rh electrocatalyst using shadow nanosphere lithography. The behaviour of the applied system in terrestrial and microgravity environment is simulated using a kinetic transport model. Differences observed for varied catalyst topography are elucidated, enabling future photoelectrode designs for use in reduced gravity environments. Y1 - 2018 U6 - https://doi.org/10.1038/s41467-018-04844-y SN - 2041-1723 IS - 9 ER - TY - GEN A1 - Brinkert, Katharina A1 - Richter, Matthias A1 - Akay, Ömer A1 - Giersig, Michael A1 - Fountaine, Katherine T. A1 - Lewerenz, Hans-Joachim T1 - Advancing semiconductor-electrocatalyst systems: application of surface transformation films and nanosphere lithography T2 - Faraday Discussions N2 - Photoelectrochemical (PEC) cells offer the possibility of carbon-neutral solar fuel production through artificial photosynthesis. The pursued design involves technologically advanced III–V semiconductor absorbers coupled via an interfacial film to an electrocatalyst layer. These systems have been prepared by in situ surface transformations in electrochemical environments. High activity nanostructured electrocatalysts are required for an efficiently operating cell, optimized in their optical and electrical properties. We demonstrate that shadow nanosphere lithography (SNL) is an auspicious tool to systematically create three-dimensional electrocatalyst nanostructures on the semiconductor photoelectrode through controlling their morphology and optical properties. First results are demonstrated by means of the photoelectrochemical production of hydrogen on p-type InP photocathodes where hitherto applied photoelectrodeposition and SNL-deposited Rh electrocatalysts are compared based on their J–V and spectroscopic behavior. We show that smaller polystyrene particle masks achieve higher defect nanostructures of rhodium on the photoelectrode which leads to a higher catalytic activity and larger short circuit currents. Structural analyses including HRSEM and the analysis of the photoelectrode surface composition by using photoelectron spectroscopy support and complement the photoelectrochemical observations. The optical performance is further compared to theoretical models of the nanostructured photoelectrodes on light scattering and propagation. KW - shadow nanosphere lithography (SNL) KW - electrocatalyst nanostructures KW - Rh electrocatalysts KW - InP photocathodes Y1 - 2018 U6 - https://doi.org/10.1039/C8FD00003D SN - 1359-6640 SN - 1364-5498 VL - 208 SP - 523 EP - 535 ER -