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In this work we show high capacity and cycle‐life performance, for electrodeposited, crystalline V2O5 thin film cathodes protected by a 1 nm ALD alumina deposit for use with Li‐metal and ionic liquid electrolyte based microbatteries. Al2O3 coatings thicker than 1 nm are shown to decrease the performance of the V2O5 thin film cathodes. The ionic liquid outperforms an organic electrolyte at 1 C rates with an initial capacity of 148 mAh g−1 and capacity retention of 97 % at cycle 50. A polymer gel analogue of the ionic liquid electrolyte in combination with the 1 nm Al2O3 coated V2O5 had an initial capacity of 139 mAh/g with a capacity retention of 93.5 % to cycle 800, illustrating high capacity and extended cycle life. [ABSTRACT FROM AUTHOR]

This work shows the electrochemical performance of sputter-deposited, binder-free lithium cobalt oxide thin films with an alumina coating deposited via atomic layer deposition for use in lithium-metal-based microbatteries. The Al2O3 coating can improve the charge–discharge kinetics and suppress the phase transition that occurs at higher potential limits where the crystalline structure of the lithium cobalt oxide is damaged due to the formation of Co4+, causing irreversible capacity loss. The electrochemical performance of the thin film is analysed by imposing 4.2, 4.4 and 4.5 V upper potential limits, which deliver improved performances for 3 nm of Al2O3, while also highlighting evidence of Al doping. Al2O3-coated lithium cobalt oxide of 3 nm is cycled at 147 µA cm−2 (~2.7 C) to an upper potential limit of 4.4 V with an initial capacity of 132 mAh g−1 (65.7 µAh cm−2 µm−1) and a capacity retention of 87% and 70% at cycle 100 and 400, respectively. This shows the high-rate capability and cycling benefits of a 3 nm Al2O3 coating. [ABSTRACT FROM AUTHOR]

Tantalum is the crucial metal of surface‐mounted (SMD) tantalum capacitors. Some 50 % of the tantalum mined is consumed in its manufacture, making waste printed circuit boards (WPCBs) an excellent source of secondary tantalum. Yet, its recycling rate is less than 1 %. This paper proposes liberating SMD capacitors from WPCBs by treating them with molten metal or salt. For both processes, the epoxy encapsulation of the capacitors did not disengage from the tantalum core. Furthermore, the molten metal process appears superior to the molten salt one. The tantalum capacitors exit the pyrolysis chamber without salt adhering to them. [ABSTRACT FROM AUTHOR]

Silicon-based heterojunction (SHJ) solar cells demonstrate high efficiencies over their homojunction counterparts, revealing the potential of such technologies. We present here the first steps towards the development of molybdenum disulfide (MoS2)/c-silicon heterojunction solar cells, consisting of a preliminary study of the MoS2 material and numerical device simulations of MoS2/Si heterojunction solar cells, using SILVACO ATLAS. Through the optical and structural characterization of MoS2/SiO2/Si samples, we found a significant sensitivity of the MoS2 to ambient oxidation. Optical ellipsometry showed a bandgap of 1.87 eV for a 7 monolayer thick MoS2 sample, suitable for the targeted application. Finally, we briefly introduce a device simulation and show that the MoS2/Si heterojunction could lead to a gain in quantum efficiency, especially in the region with short wavelengths, compared with a standard a-Si/c-Si solar cell. [ABSTRACT FROM AUTHOR]

A surface sensitivity study was performed on different transition-metal dichalcogenides (TMDs) under ambient conditions in order to understand which material is the most suitable for future device applications. Initially, Atomic Force Microscopy and Scanning Electron Microscopy studies were carried out over a period of 27 days on mechanically exfoliated flakes of 5 different TMDs, namely, MoS2, MoSe2, MoTe2, HfS2, and HfSe2. The most reactive were MoTe2 and HfSe2. HfSe2, in particular, showed surface protrusions after ambient exposure, reaching a height and width of approximately 60 nm after a single day. This study was later supplemented by Transmission Electron Microscopy (TEM) cross-sectional analysis, which showed hemispherical-shaped surface blisters that are amorphous in nature, approximately 180-240 nm tall and 420-540 nm wide, after 5 months of air exposure, as well as surface deformation in regions between these structures, related to surface oxidation. An X-ray photoelectron spectroscopy study of atmosphere exposed HfSe2 was conducted over various time scales, which indicated that the Hf undergoes a preferential reaction with oxygen as compared to the Se. Energy-Dispersive X-Ray Spectroscopy showed that the blisters are Se-rich; thus, it is theorised that HfO2 forms when the HfSe2 reacts in ambient, which in turn causes the Se atoms to be aggregated at the surface in the form of blisters. Overall, it is evident that air contact drastically affects the structural properties of TMD materials. This issue poses one of the biggest challenges for future TMD-based devices and technologies. [ABSTRACT FROM AUTHOR]

Capacitance-Voltage (C-V) characterization and hard x-ray photoelectron spectroscopy (HAXPES) measurements have been used to study metal/Al2O3/In0.53Ga0.47As capacitor structures with high (Ni) and low (Al) work function metals. The HAXPES measurements observe a band bending occurring prior to metal deposition, which is attributed to a combination of fixed oxide charges and interface states of donor-type. Following metal deposition, the Fermi level positions at the Al2O3/In0.53Ga0.47As interface move towards the expected direction as observed from HAXPES measurements. The In0.53Ga0.47As surface Fermi level positions determined from both the C-V analysis at zero gate bias and HAXPES measurements are in reasonable agreement. The results are consistent with the presence of electrically active interface states at the Al2O3/In0.53Ga0.47As interface and suggest an interface state density increasing towards the In0.53Ga0.47As valence band edge. [ABSTRACT FROM AUTHOR]

In this work, we present the results of an investigation into charge trapping in metal/high-k/In0.53Ga0.47As metal-oxide-semiconductor capacitors (MOS capacitors), which is analysed using the hysteresis exhibited in the capacitance-voltage (C-V) response. The availability of both n and p doped In0.53Ga0.47As epitaxial layers allows the investigation of both hole and electron trapping in the bulk of HfO2 and Al2O3 films formed using atomic layer deposition (ALD). The HfO2/In0.53Ga0.47As and Al2O3/In0.53Ga0.47As MOS capacitors exhibit an almost reversible trapping behaviour, where the density of trapped charge is of a similar level to high-k/In0.53Ga0.47As interface state density, for both electrons and holes in the HfO2 and Al2O3 films. The experimental results demonstrate that the magnitude of the C-V hysteresis increases significantly for samples which have a native oxide layer present between the In0.53Ga0.47As surface and the high-k oxide, suggesting that the charge trapping responsible for the C-V hysteresis is taking place primarily in the interfacial oxide transition layer between the In0.53Ga0.47As and the ALD deposited oxide. Analysis of samples with a range of oxide thickness values also demonstrates that the magnitude of the C-V hysteresis window increases linearly with the increasing oxide thickness, and the corresponding trapped charge density is not a function of the oxide thickness, providing further evidence that the charge trapping is predominantly localised as a line charge and taking place primarily in the interfacial oxide transition layer located between the In0.53Ga0.47As and the high-k oxide. [ABSTRACT FROM AUTHOR]

In this paper, we designed, fabricated and tested a microwave circuit based on a MoS2 self-switching diode. The MoS2 thin film (10-monolayers nominal thickness) was grown on a 4 inch Al2O3/high-resistivity silicon wafer by chemical vapor deposition process. The Raman measurements confirm the high quality of the MoS2 over the whole area of the 4 inch wafer. We show experimentally that a microwave circuit based on a few-layers MoS2 self-switching diode fabricated at the wafer level is able to detect the audio spectrum from amplitude-modulated microwave signals in the band 0.9–10 GHz, i.e. in the frequency range mostly used by current wireless communications. In particular, the 900 MHz band is widely exploited for GSM applications, whereas the 3.6 GHz band has been identified as the primary pioneer band for 5G in the European Union. [ABSTRACT FROM AUTHOR]