Dielectric Passivation Research Articles

The influence of inner material with different average thermal conductivity on the performance of whole insulation system for liquid hydrogen on orbit storage

At present, several composite insulation systems were proposed that can be used for passive insulation systems, including foam-variable density multilayer insulation (VDMLI), aerogel-VDMLI and hollow glass microspheres (HGMs)-VDMLI. The passive insulation systems with different inner material (IM) showed different performances. However, the relationship between the average thermal conductivity of IM and the insulation performance of the whole system has rarely been investigated. It is of great significance for efficient configuration and matching of the passive insulation system. In this paper, a series of average thermal conductivity of IM were assumed to predict the insulation performance of the whole system at 20 K–300 K and high vacuum. In order to further illustrate the relationship between IM and MLI/VDMLI, the foam was replaced by the HGMs as 5 mm a unit forming a series of HGMs-foam-MLI/VDMLI insulation systems. The performance of the systems was investigated. After the foam was completely replaced by the HGMs, the performance of MLI and VDMLI systems was improved 33% and 13%, respectively. Moreover, each mode of heat transfer including solid conduction, radiation, and gas conduction for foam-MLI/VDMLI and HGMs-MLI/VDMLI insulation systems were calculated and analyzed.

Clean-Room Lithographical Processes for the Fabrication of Graphene Biosensors.

This work is on developing clean-room processes for the fabrication of electrolyte-gate graphene field-effect transistors at the wafer scale for biosensing applications. Our fabrication process overcomes two main issues: removing surface residues after graphene patterning and the dielectric passivation of metallic contacts. A graphene residue-free transfer process is achieved by using a pre-transfer, sacrificial metallic mask that protects the entire wafer except the areas around the channel, source, and drain, onto which the graphene film is transferred and later patterned. After the dissolution of the mask, clean gate electrodes are obtained. The multilayer SiO2/SiNx dielectric passivation takes advantage of the excellent adhesion of SiO2 to graphene and the substrate materials and the superior impermeability of SiNx. It hinders native nucleation centers and breaks the propagation of defects through the layers, protecting from prolonged exposition to all common solvents found in biochemistry work, contrary to commonly used polymeric passivation. Since wet etch does not allow the required level of control over the lithographic process, a reactive ion etching process using a sacrificial metallic stopping layer is developed and used for patterning the passivation layer. The process achieves devices with high reproducibility at the wafer scale.

PP352 Systematic Review Of Clinical Effects Of Different Thermal Insulation Measures In Patients Undergoing Major Surgery

IntroductionHypothermia (core temperature <36°C) during major surgeries could result in a number of adverse events such as surgical site infection, bleeding, and prolonged hospital stay. The incidence of intraoperative hypothermia was 44.3 percent in China in 2015, with only 10.7 percent of patients receiving effective hypothermia prevention measures during major surgeries. By systematically examining the adverse risks for patients using different warming measures (active and passive), our study discussed the potential of bringing the most effective one(s) into clinical guidelines.MethodsArticles, ongoing trials and grey literatures were retrieved from PubMed, The Cochrane Library and Clinical Trials till February 2019. Bair HuggerTM (BH) was determined to be the reference group and all randomized controlled trials including BH were included. In the control group, we kept all possible warming measures. Adverse effect indicators were decided using scoping reviews and then applied in literature screening. Type (open/endoscopic) and length of surgery were included in sub-group analysis.ResultsA total of forty-two studies were included, with twenty-seven of them passive insulation measures and fifteen active measures. Compared with passive measures, BH had significant advantages, such as in surgical site infection (risk ratio [RR] = 0.13, 95% confidence interval [CI]: 0.05, 0.80), chills (RR = 0.37, 95% CI: 0.25, 0.54) and hospitalization stay (mean difference [MD]=−1.27d, 95% CI: -2.05, -0.48). Compared with active insulation measures, BH had no significant advantages. Patients with open or longer surgeries (≥2 hours) experienced higher risks.ConclusionsGenerally, an active warming system is more effective in lowering risks (e.g., hypothermia, surgical site infection, chills, length of stay) than passive ones, especially for patients going through non-endoscopic or longer surgeries. Among the active warming systems, BH does the same job as other active insulation measures. Given that the practice of peri-operative hypothermia prevention using active warming systems is not popular in China, the use of BH and other active insulation measures during major surgeries are recommended to improve the safety and potentially reduce the cost of treating those clinical adverse events.

Graphene Functionalization As a Seed for Dielectric Passivation

Two-dimensional (2D) semiconductor materials like Transition Metal Dichalcogenides (TMDCs) are prominent candidates to replace silicon (Si) as channel material in the future (Si-based) transistors. However, to fully exploit the superior properties of 2D TMDCs, their inherent problem of basal-plane inertness needs to be resolved to enable dielectric passivation layer growth. Therefore, the objective of this work is to explore innovative options to enable high-k growth on 2D materials.A literature study is provided, setting out how 2D materials became of interest to the microelectronic industry as a results of continuous device downscaling. To overcome the issue of basal plane inertness, a single layer graphene is used that acts as a sacrificial growth template. This graphene layer is deposited on top of a base layer (e.g. 2D material), whereby the graphene layer is chemically activated via a dry UV/ozone treatment, while preserving the properties of the underlying 2D layer.Initial experiments focus on the removal of polymer-based transfer residues that typically remain on the graphene surface after transfer. Mechanical scratching atomic force microscopy shows that hydrogen plasma treatments are an effective and time-efficient method to remove polymer transfer residues. However, the plasma exposure also induces surface modifications as demonstrated by Raman characterization.Next, the growth template is chemically activated by gently oxidizing the graphene layer via a dry UV/ozone treatment. The UV/ozone process characteristics are explored in function of the graphene cleaning treatments developed in the previous stage. For as-received graphene an operating window of 2-5 minutes of UV/ozone exposure is defined in order to maximize the oxidation degree, and thus nucleation sites. Activation is in balance with graphene layer damage or removal. The process is evaluated based on contact angle measurements, Raman and conductivity atomic force microscopy characterization.Lastly, an atomic layer deposition study is carried out that focuses on high-k deposition on the activated single layer graphene to provide a proof-of-concept of enhanced dielectric growth in function cleaning and activation treatments developed in the preceding stages. Rutherford backscattering spectroscopy demonstrates the importance of a well-functionalized surface to achieve good material growth.

A high-efficiency liquid hydrogen storage system cooled by a fuel-cell-driven refrigerator for hydrogen combustion heat recovery

Effective thermal insulation technology is served as the key to liquid hydrogen storage. Existing studies have mainly been shedding light on the performance optimization of the passive thermal insulation systems or the direct introduction of refrigerators to achieve zero-boil-off storage. However, considering the immense combustion heat that is taken away by gaseous hydrogen discharged from the passive thermal insulation system, and the additional electric power required to be introduced in driving the refrigerator under the current zero-boil-off system, this paper is intended to propose a novel liquid hydrogen storage system that is cooled by a fuel-cell-driven refrigerator for hydrogen combustion heat recovery. In an effort to reduce the heat leakage, the combustion heat is recovered and converted into electricity, which can then be used to drive the refrigerator in cooling the passive insulation material. In this paper, a thermodynamic calculation model composite of the fuel cell, refrigerator, and passive thermal insulation system was established and verified. According to the results, at a fuel cell efficiency of 50%, the insulation efficiency of the proposed system is improved by up to 80.3% compared with the traditional multi-layer insulation system. Besides, the effects of fuel cell efficiency, refrigerator efficiency, cold shield position, storage pressure, boundary temperature, and system vacuum on the insulation performance were also analyzed.

Flow Assurance Study on Offshore Marginal Oil Field Development in Vietnam: The Case of Ca Ngu Vang Oil Field

Over the last few years, PetroVietnam has discovered and exploited several marginal oil fields such as Ca Ngu Vang, Te Giac Trang, Hai Su Den, Hai Su Trang, etc. however the reserves are modest. Test results received during drilling exploratory wells within these fields indicated that the maximum total daily production rate from the wells could promisingly range to about 20,000 barrels of oil per day (BOPD). Unfortunately, the optimum development of these offshore oil fields still offers numerous challenges to oil engineers due to the limitations of equipment and technology. Oil production activities worldwide show that if the daily production of an offshore oilfield is less than 20,000 BOPD, a connection of the marginal fields to their nearest larger oil field should be taken into consideration in order to efficaciously recover more crude oil. Often, this method of production requires a long subsea pipeline system. Besides, the transportation of the fluids from these fields to the processing platform will undergo several serious problems caused by the deposition of wax. All these matters should be handled to guarantee the performance of transportation. A number of models using PIPESIM, PIPEPHRASE and OLGA have been applied to design and examine the operations of the subsea pipeline in different working conditions. Results of the simulations proposed the use of passive insulation to economically eliminate wax deposition and recommended proper pipeline shutdown operations to minimize several problems related to flow assurance issues in the region of interest.

Thermal suit connected to a forced-air warming unit for preventing intraoperative hypothermia: A randomised controlled trial.

Inadvertent intraoperative hypothermia is a common occurrence in surgical patients. A thermal suit is an option for passive insulation. However, active warming is known to be more effective. Therefore, we hypothesised that a forced-air warming (FAW) unit connected to the thermal suit is superior to a commercial FAW blanket and a warming mattress in breast cancer surgery. Forty patients were randomised to this prospective, clinical trial to wear either the thermal suit or conventional hospital clothes under general anaesthesia. The Thermal suit group had a FAW unit set to 38°C and connected to the legs of the suit. The Hospital clothes group had a lower body blanket set to 38°C and a warming mattress set to 37°C. Core temperature was measured with zero-heat-flux sensor. The primary outcome was core temperature on admission to the recovery room. There was no difference in mean core temperatures at anaesthetic induction (P=.4) or on admission to the recovery room (P=.07). One patient in the Thermal suit group (5%) vs six patients in the Hospital clothes group (32%) suffered from intraoperative hypothermia (P=.04, 95% CI 1.9%-49%). Mean skin temperatures (MSTs) were higher in the Thermal suit group during anaesthesia. No burns or skin irritations were reported. Two patients in the Thermal suit group sweated. A thermal suit connected to a FAW unit was not superior to a commercial FAW blanket, although the incidence of intraoperative hypothermia was lower in patients treated with a thermal suit.

Active Control of Low-Frequency Noise through a Single Top-Hung Window in a Full-Sized Room

The push for greater urban sustainability has increased the urgency of the search for noise mitigation solutions that allow for natural ventilation into buildings. Although a viable active noise control (ANC) solution with up to 10 dB of global attenuation between 100 Hz and 1000 Hz was previously developed for an open window, it had limited low-frequency performance below 300 Hz, owing to the small loudspeakers used. To improve the low-frequency attenuation, four passive radiator-based speakers were affixed around the opening of a top-hung ventilation window. The active control performance between 100 Hz and 700 Hz on a single top-hung window in a full-sized mock-up apartment room was examined. Active attenuation came close to the performance of the passive insulation provided by fully closing the window for expressway traffic and motorbike passing noise types. For a jet aircraft flyby, the performance of active attenuation with the window fully opened was similar to that of passive insulation with fully closed windows. In the case of low-frequency compressor noise, active attenuation’s performance was significantly better than the passive insulation. Overall, between 8 dB and 12 dB of active attenuation was achieved directly in front of the window opening, and up to 10.5 dB of attenuation was achieved across the entire room.

Experimental Study on Mitigation of Lifetime-Limiting Dielectric Cracking in Extreme Temperature 4H-SiC JFET Integrated Circuits

While NASA Glenn Research Center’s “Generation 10” 4H-SiC Junction Field Effect Transistor (JFET) integrated circuits (ICs) have uniquely demonstrated 500 °C electrical operation for durations of over a year, this experimental work has also revealed that physical cracking of chip dielectric passivation layers ultimately limits extreme-environment operating lifetime [1-3]. The prevention of such dielectric passivation cracks should therefore improve IC high temperature durability and yield, leading to more beneficial technology adoption into aerospace, automotive, and energy systems. This report describes Generation 10.2, 11.1, and 11.2 die tested under unbiased and unpackaged accelerated age testing at 500 °C, 600 °C, 720 °C, and 800 °C in air-atmosphere ovens for 100-and 200-hour duration. Additional samples were separately subjected to 10 thermal cycles between the same high temperatures (with 10-hour high-temperature soak each cycle) and 50 °C. It is shown that having two stoichiometric Si3N4 layers in the interconnect dielectric stack substantially decreases the amount of dielectric cracking observed following these oven tests.

Molybdenum oxide on carbon nanotube: Doping stability and correlation with work function

Carbon nanotubes (CNTs) have great potential for future high-performance and energy-efficient transistor technology. To realize this potential, methods to dope the CNTs need to be developed to achieve low parasitic resistance of the transistor. Two key issues present themselves: (a) understanding the doping mechanism of the various methods and (b) stability of the doping method. For instance, although studies on molybdenum oxide (MoOx) demonstrate its ability to heavily dope nanomaterials, the interaction between MoOx and the CNT is unclear. Here, we observe an unstable effect of MoOx on the CNT and demonstrate dielectric passivation as a means to preserve the doping strength. The semiconducting CNTs exhibit greater than 103× reduction in resistance after stably doped with MoOx. By exploiting the instability of MoOx, we delve deeper into clarifying the doping mechanism. The relationship between the time-dependent material property of MoOx and the change in the electrical measurements of CNT devices is investigated to study the role of work function in doping the CNTs. We conclude that the doping mechanism of MoOx on the CNT is due to bandgap modulation by charge transfer, which occurs due to the difference in work function between MoOx and the CNT.

Optimization of passivation in AlGaN/GaN heterostructure microwave transistor fabrication by ICP CVD

We have studied the effect of silicon nitride (SiN) dielectric passivating film deposition by inductively coupled plasma chemical vapor deposition (ICP CVD) on the parameters of AlGaN/GaN heterostructure high electron mobility transistors (HEMT). Study of the parameters of the dielectric layers has allowed us to determine the effect of RF and ICP power and working gas flow ratio on film growth rate and structural perfection, and on the current vs voltage curves of the passivated HEMT. The deposition rate changes but slightly with an increase in RF power but increases with an increase in ICP power. Transistor slope declines considerably with an increase in RF power: it is the greatest at minimum power RF = 1 W. In the beginning of growth even at a low RF power (3 W) the transistor structure becomes completely inoperable. Dielectric deposition for HEMT passivation should be started at minimum RF power. We have developed an AlGaN/GaN microwave HEMT passivation process providing for conformal films and low closed transistor drain–source currents without compromise in open state transistor performance: within 15 and 100 mA, respectively, for a 1.25 and 5 mm common T-gate (Ug = –8 V and Ud-s = 50 V).

Empirical investigation to explore potential gains from the amalgamation of phase changing materials (PCMs) and wood shavings

• Panels containing PCM, Wood-shaving and PCM/wood-shavings amalgams are created. • Panels are subjected to heat profiles and their thermal performances were compared. • Heat peak reduction, heat peak shift and fluctuation of temperatures are examined. • Amalgamation of wood-shavings did not improve the PCM's thermal performance. • The overall weight of the panels was reduced due to amalgamating wood-shavings. The reduction of gained heat, heat peak shifting, and the mitigation of air temperature fluctuations are some desirable properties that are sought after in any thermal insulation system. It cannot be overstated that these factors, in addition to others, govern the performance of such systems thus their effect on indoor ambient conditions. The effect of such systems extends also to Heating, Ventilation and Air-conditioning (HVAC) systems that are set up to operate optimally in certain conditions. Where literature shows that PCMs and natural materials such as wood-shavings can provide efficient passive insulation for buildings, it is evident that such approaches utilise methods that are of a degree of intricacy which require specialist knowledge and complex techniques, such as micro-encapsulation for instance. With technical and economic aspects in mind, an amalgam of PCM and wood-shavings has been created to be utilised as a feasible thermal insulation. The amalgamation was performed in the simplest of methods, through submerging the wood shavings in PCM. An experimental procedure was devised to test the thermal performance of the amalgam and compare this to the performance of the same un-amalgamated materials. Comparative analysis revealed that no significant thermal gains would be expected from such amalgamation. However, a significant reduction in the total weight of the insulation system would be achieved that, in this case, shown to be up to 20.94%. Thus, further reducing possible strains on structural elements due to the application of insulation on buildings. This can be especially beneficial in vernacular architectural approaches where considerably large amounts and thicknesses of insulations are used. In addition, cost reduction could be attained as wood shavings are significantly cheaper compared to the cost of PCMs.

Revealing the importance of light extraction efficiency in InGaN/GaN microLEDs via chemical treatment and dielectric passivation

Chemical etching and Al2O3 dielectric passivation were used to minimize nonradiative sidewall defects in InGaN/GaN microLEDs (mesa diameter = 2–100 μm), resulting in an increase in external quantum efficiency (EQE) as the LED size was decreased. Peak EQEs increased from 8%–10% to 12%–13.5% for mesa diameters from 100 μm to 2 μm, respectively, and no measurable leakage currents were seen in current density–voltage (J–V) characteristics. The position and shape of EQE curves for all devices were essentially identical, indicating size-independent ABC model (Shockley–Read–Hall, radiative, and Auger recombination) coefficients-behavior that is not typical of microLEDs as the size decreases. These trends can be explained by enhancement in light extraction efficiency (LEE), which is only observable when sidewall defects are minimized, for the smallest LED sizes. Detailed ray-tracing simulations substantiate the LEE enhancements.

Charge fluctuations at the Si–SiO2 interface and its effect on surface recombination in solar cells

The Si–SiO2 interface has and will continue to play a major role in the development of silicon photovoltaic devices. This work presents a detailed examination of how charge at or near this interface influences device performance. New understanding is identified on the effect of charge-induced potential fluctuations at the silicon surface. Such fluctuations have been considered in Si–SiO2 recombination models previously, where a universal value of electrical potential deviation was used to represent the effect. However, the approach disregards that the variation occurs in the charge concentration rather than the potential. We modify the models to accurately reflect fluctuations in external charge, allowing a precise representation of surface recombination velocity, with self-consistent Dit, σp, and σn parameters. Correctly accounting for these parameters can provide insights into the passivation mechanisms which can aid the development of future devices. Using the corrected model, we find that the effect of charge fluctuation at the Si–SiO2 interface is significant for the depletion regime to the weak inversion regime. This indicates that surface passivation dielectrics must operate with charge concentrations in excess of 2x1012 q/cm2 to avoid these effects. TCAD device simulations show that the efficiency of future PERC cells can improve up to 1% absolute when optimally charged dielectric coatings are applied both at the front and rear surfaces.

GAN –STRUCTURE AND FABRICATION TECHNIQUES- A COMPREHENSIVE REVIEW

HEMT (High Electron Mobility Transistor) Gallium Nitride (GaN), a heterostructure semiconductor with huge potential for fostering economic development in a silicon-based electronics industry, is currently facing growing production versus investment costs. The high intensity of the electric field and the mobility of electrons have previously demonstrated enormous potential for multi-gigahertz frequency communications and photonic applications at material level. Productivity developments on commercially viable wide area substrates are now at the marketing stage where GaN power conversion technologies are on the verge of available for market. The prospect to build on the research outlined here is very interesting in ways informed by unique problems emerging out of entirely advanced markets and applications. Hence, this series of innovation in GaN technology is not itself a road map, but a valuable set of state-of-the-art international GaN research that guides the next development process as market-driven needs evolve. Industrial companies make significant investments in a wide range of sector identifying the use of innovation in new circuit designs, packaging technologies and system level interfacing required to achieve and maximize the product benefits provided by GaN transistors. AlN / GaN MOS-HEMTs process layout is dealt with problems and challenges in the manufacturing process. The advanced technology is using Al2O3 thermally grown as a dielectric gate and system surface passivation. Significant improvement in system efficiency seen using Ohmic contact optimization and mesa sidewall passivation are elaborated. This paper describes and analyzes the DC and RF efficiency of the semiconductor switch and it is concluded that a GaN device with enhancement mode with a vertical structure is preferred as it has numerous advantages. These GaN devices are now employed in the field operating within power supplies and motor controls for industrial, commercial, and automotive applications, in addition to their recognition and reputation.

Designing Beveled Edge Termination in GaN Vertical p-i-n Diode-Bevel Angle, Doping, and Passivation

A series of electric field profile simulations in gallium nitride (GaN) p-i-n vertical diodes with negative bevel termination is carried out to optimize the bevel design. The bevel angles are varied from 90° to 0.1° with reasonably small increments to study the impact of the bevel angle on the electric field profile. The doping densities are also varied to study a more generalized trend; a new parameter defined as transition angle $\theta _{{\text {t}}}$ is proposed to characterize the effectivity of a beveled edge termination. Considering the potential dry etch damage on the bevel side-wall during device fabrication, the fixed surface charge from the dangling bonds and commonly used dielectric passivation are also added separately to investigate their influence. This article presents a comprehensive simulation study of GaN p-i-n diode with negative beveled edge termination, making it a useful guide for designing a simple and effective beveled edge termination, which eventually helps to enable the routine avalanche in GaN p-i-n diodes.

Oxidation as Key Mechanism for Efficient Interface Passivation in Cu(In,Ga)Se2 Thin-Film Solar Cells

Author(s): Werner, F; Veith-Wolf, B; Spindler, C; Barget, MR; Babbe, F; Guillot, J; Schmidt, J; Siebentritt, S | Abstract: Copper-indium-gallium-diselenide (CIGS) thin-film solar cells suffer from high recombination losses at the back contact and parasitic absorption in the front-contact layers. Dielectric passivation layers overcome these limitations and enable an efficient control over interface recombination, which becomes increasingly relevant as thin-film solar cells increase in efficiency and become thinner to reduce the consumption of precious resources. We present the optoelectronic and chemical interface properties of oxide-based passivation layers deposited by atomic layer deposition on CIGS. A suitable postdeposition annealing removes detrimental interface defects and leads to restructuring and oxidation of the CIGS surface. The optoelectronic interface properties are very similar for different passivation approaches, demonstrating that an efficient suppression of interface states is possible independent of the metal used in the passivating oxide. If aluminum oxide (Al2O3) is used as the passivation layer we confirm an additional field-effect passivation due to interface charges, resulting in an efficient interface passivation superior to that of a state-of-the-art cadmium-sulfide (CdS) buffer layer. Based on this chemical interface model we present a full-area rear-interface passivation layer without any contact patterning, resulting in a 1% absolute efficiency gain compared to a standard molybdenum back contact.

(Invited) Materials for Power Electronics – the Role of Defects and Dielectric Passivation

SiC and GaN are the main semiconductor materials for current power electronics [1,2]. In this contribution, we will review our efforts to realize a complete chain of material characterization stretching from characterization of point defects, impurities and strain, passivation by thin dielectric films to device fabrication for wide band gap devices. For a better device performance, a detailed understanding of the defects contained in the material and the passivation capability of dielectric layers, hence the formed interface defect states is mandatory. We will show the impact of SiC and GaN defect states on the minority carrier lifetime and their luminescence behavior. Interestingly, we find a stretched exponential decay in the lifetime measurements on free standing 4H-SiC, which hints at a temperature activated carrier migration effect contributing to the near band edge luminescence signal quenching/band-to-band carrier recombination [3]. In addition, the role of different dopant elements on the luminescence behavior of GaN was investigated focusing on transition metal [4,5] and carbon doping [6], which experiences new interest due to potential application for quantum computation [7] and novel electronic properties [8]. In the case of GaN the semiconductor–high-k dielectric interface was investigated in detail and the integration in so called MISHEMT (metal-insulator-semiconductor high electron mobility transistors) with different dielectrics and varying thermal budgets could be shown. Here, the impact of a fully amorphous dielectric (Al2O3), which was kept amorphous by the integration of a low thermal budget ohmic contact [9], was compared to an epitaxial dielectric (GdScO) [10]. By this, a reduction of the trapping behavior of the devices could be shown, achieved by an excellent chemical passivation and a detailed band alignment engineering between dielectric layer and semiconductor material.[1] Yole Developpement,RF GaN Market: Applications, Players, Technology andSubstrates 2019, Market & Technology Report, May2019[2] T. Kimoto, Jpn. J. Appl. Phys. 54, 40103 (2015).[3] Beyer, J., Heitmann, J., Schüler, N., Dornich, K., Kato, M., EMRS spring meeting 2019, Nice, France.[4] Zimmermann, F., Gärtner, G., Sträter, H., Röder, C., Barchuk, M., Bastin, D., Hofmann, P., Krupinski, M., Mikolajick, T., Heitmann, J., Beyer, F.C.; Journal of Luminescence, 207 (2019) 507-511.[5] Zimmermann, F., Beyer, F.C., Gärtner, G., Röder, C., Son, N.T., Janzén, E., Veselá, D., Lorinčík, J., Hofmann, P., Krupinski, M., Mikolajick, T., Habel, F., Leibiger, G., Heitmann, J; Optical Materials, 70 (2017) 127-130.[6] Richter, E.; Beyer, C. F.; Zimmermann, F.; Gärtner, G.; Irmscher, K.; Gamov, I.; Heitmann, J.; Weyers, M.; Tränkle, G.: Cryst. Res. Technol.2019, 190012[7] W. F. Koehl, B. Diler, S. J. Whiteley, A. Bourassa, N. T. Son, E. Janzen, and D.D. Awschalom, PRB 95, 035207 (2017).[8] Tanaka, N. Kaneda, T. Mishima, Y. Kihara, T. Aoki, K. Shiojima, Jpn.J. Appl. Phys.2015,54, 041002.[9] Schmid, A.; Schröter, Ch.; Otto, R.; Schuster, M.; Klemm, V.; Rafaja, D.; Heitmann, J., Appl. Phys. Lett. 106, 053509 (2015)[10] Seidel, S., Schmid, A., Miersch, C., Schubert, J., Heitmann, J. IWN 2018, Kanazawa, Japan.

Silicon Solar Cells: Conductive Hole‐Selective Passivating Contacts for Crystalline Silicon Solar Cells (Adv. Energy Mater. 16/2020)

In article number 1903851, Jianhui Chen and co-workers discern a region of good conductivity and passivation in a passivation-conductivity phase-like diagram, which enables conductive passivating contacts for silicon solar cells. This work suggests a low-cost surface engineering strategy for future photovoltaic technologies, with the advantage of omitting the use of conventional dielectric passivation materials and simplifying the fabrication process.

Thermal and Electrical Properties of Isocyanate Derived Organic Aerogels for Cryogenic Insulation Applications

The use and storage of cryogens such as liquefied nitrogen, helium, hydrogen among others requires reliable and efficient thermal insulation systems. Passive insulation from high performance materials that are well-known for their inherent low thermal conductivity would reduce the overall costs involved in design, manufacture and maintenance of such systems. One such class of materials are referred to as aerogels. These materials are known for their low density, high mesoporosity, high surface areas, low thermal conductivity and high acoustic impedance. Aerogels were invented by S.S. Kistler in 1931 and the most common type are those made of silica. However, the inherent fragility of silica aerogels makes them hard to mass produce, and therefore applications have been limited. A major breakthrough was introduced by our team almost 20 years ago with the invention of polymer crosslinked silica aerogels. Those materials shifted attention to all-polymer aerogels that have overcome all fragility issues associated with their inorganic counterparts. This study focuses on such polymeric aerogels that can be mass produced as large monoliths while maintaining the low thermal conductivity of traditional silica aerogels over a wide temperature range. Manufacturing flexibility of polymeric aerogels allows fabrication of blocks and sheets that can be applied in various configurations to insulate cryogenic and superconducting devices. The thermal conductivity with 80 K and room temperature boundary are reported as well as other properties (electrical), that need to be considered when designing devices for cryogenic applications.