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We demonstrate an Nb 2 O 5 / β - Ga 2 O 3 metal–insulator–semiconductor (MIS) hetero-junction diode with Nb 2 O 5 as the high-k dielectric insulator for more efficient electric field management resulting in enhanced breakdown characteristics compared to a β - Ga 2 O 3 Schottky barrier diode. Nb 2 O 5 dielectric films were grown using atomic layer deposition and exhibited a high dielectric constant of 50. The high dielectric constant resulted in a 5 × lower electric field at the metal/dielectric interface in the MIS diode compared to the metal/ β - Ga 2 O 3 interface in the Schottky barrier diode. With good electron conduction in forward bias enabled by the negative conduction band offset of Nb 2 O 5 with respect to β - Ga 2 O 3 , the MIS design led to a 3 × improvement in the reverse blocking voltage with a slight trade-off in the specific on-resistance. Overall, a 3.3 × increase in the power figure of merit was observed (3.25 MW / cm 2 for the Schottky diode and 10.8 MW / cm 2 for the MIS diode). A detailed analysis of the energy band line-up and the forward and reverse current transport mechanisms are also presented using analytical modeling and 2D technology computer-aided design simulations. [ABSTRACT FROM AUTHOR]

Ternary dielectrics with varying composition formed by alloying two binary oxides can enable tunable optical and electrical properties for advanced technological applications. Atomic layer deposition (ALD) gives precise control over ternary dielectric composition through the ability to finely tune the precursor pulsing ratio. This work presents ALD development of Si-rich SixTi1−xO2 dielectrics with varying composition (x), along with spectroscopic and electrical characterization of their properties. Stoichiometry of the SixTi1−xO2 films was determined using X-ray photoelectron spectroscopy. Their composition-dependent refractive index, energy bandgap, and reflectance show promise for diverse optical applications ranging from anti-reflective coatings in photovoltaics to optical waveguides. This work also reports a first comparative study of SixTi1−xO2 films prepared by thermal (T-) and plasma-enhanced (PE-) ALD with varying Si composition and deposition temperatures. Deposition rates of 0.67–0.92 Å/cycle were obtained for SixTi1−xO2 films with x = 0.5–0.91 deposited using PE-ALD at 250 °C, which were higher than that of T-ALD at 200 °C (0.42–0.05 Å/cycle). PE-ALD also exhibited a high deposition rate of 0.81 Å/cycle for SixTi1−xO2 film with x = 0.91 at a low growth temperature of 150 °C. The PE-ALD Si-rich silica–titania films show substantially lower (100×) leakage current densities than the thermally deposited films, along with higher breakdown fields for decreasing deposition temperature. A dielectric constant as low as ∼5 was achieved for PE-ALD SixTi1−xO2 films with high Si (x = 0.91) content. [ABSTRACT FROM AUTHOR]

Fin field-effect transistor (FinFET) scaling beyond the 10-nm node requires formation of a junction isolation region between the source and the drain to suppress sub-fin leakage current. In this paper, heavy species such as Sb and As were implanted at room temperature to form a punch-through stop (PTS) layer in ${n}$ -Ge substrates. The impact of PTS implants on channel doping and defects, as well as junction leakage, was investigated for bulk Ge ${p}$ -FinFET applications. We report retrograde doping profiles with a low surface (channel) dopant concentration of 4–5 $\times 10^{\textsf {16}}$ cm−3 for Sb PTS implants post 550 °C and 650 °C activation anneals. Besides achieving low effective channel doping, the 650 °C high-temperature activation anneal post PTS implant also helps in the reduction of channel defect density. Furthermore, low junction leakage currents are also demonstrated for Sb and As PTS implants with 550 °C and 650 °C activation anneals. To avoid damaging the FinFET channel layer due to PTS ion implantation, Ge homoepitaxy was also studied post Sb PTS implants. However, Sb PTS implants activated at 650 °C without Ge epitaxy exhibit the best results in terms of low channel dopant and defect concentrations, besides junction leakage. [ABSTRACT FROM AUTHOR]

This work demonstrates a solution to the problem of increase in Schottky barrier height (#8709;B) with thermal annealing (thermal instability) in unpinned (low #8709;B) Ti/TiO2/n-Ge metal-interfacial layer (IL)-semiconductor (MIS) contacts through plasma nitridation of the TiO2 layer. Unlike TiO2, unpinned (#8709;B =0.09 eV) TiOxNy contacts are thermally stable for anneals up to 30 min at 400°C. The thermal stability improves with increasing nitrogen concentration ([N], 2.5-9.5%) and is independent of thickness (2-5 nm) for [N]=9.5%. Additionally, the plasma nitridation process is shown to increase the oxygen vacancy concentration (n-type doping) and reduce the #8709;B dependence on TiOxNy thickness in unannealed TiOxNy contacts. Enhanced thermal stability is attributed to the incorporated nitrogen acting as a diffusion barrier that prevents contact pinning through reduction of the TiO2 layer by contact metal during the anneal, as well as preserves the amorphous nature of the IL along with its fixed charge and interfacial dipoles that contribute to #8709;B reduction. [ABSTRACT FROM AUTHOR]

β-Ga2O3 based enhancement mode transistor designs are critical for the realization of low loss, high efficiency next generation power devices with rudimentary driving circuits. A large positive flatband voltage (Vfb) of 10.6 V in β-Ga2O3 metal-oxide-semiconductor capacitors, with the ability to fine-tune it between 3.5 V and 10.6 V, using a polycrystalline AlN charge trap layer has been demonstrated. This can enable enhancement mode operation over a wide doping range. An excellent Vfb retention of ∼ 97% for 104 s at 55 °C was exhibited by the gate stacks after charge trapping, hence reducing the requirement of frequent charge injection cycles. In addition, low gate leakage current density (Jg) for high negative gate voltages (Vg ∼ −60 V) indicates the potential of this gate stack to enable superior breakdown characteristics in enhancement mode transistors. [ABSTRACT FROM AUTHOR]

High performance gate stacks are critically needed for the development of β-Ga2O3 power transistors. Significant improvement in the performance of β-Ga2O3 gate stacks is demonstrated in this work by using SiO2 as an interlayer dielectric between Al2O3 and β-Ga2O3. The presence of SiO2 results in an 800× reduction in gate leakage current along with a 1.7× increase in the electric breakdown field. Additionally, the capacitance-voltage characteristics show an increase in flat band voltage (from 0.74 V to 3.25 V) that can enable normally off power transistors. The lowest interface trap density (Dit) of 5.1 × 1010 cm−2 eV−1 for the SiO2/β-Ga2O3 interface has been demonstrated through the use of a piranha clean before SiO2 deposition on β-Ga2O3 for the first time. Reduction (8×) in Dit, hysteresis (from 0.17 V to 0.05 V), and border trap density indicate substantial improvement in the quality of the β-Ga2O3/gate dielectric interface for the Al2O3/SiO2 bilayer stack as compared to only Al2O3. [ABSTRACT FROM AUTHOR]

Single mode (either T 1 or T 2) contrast agents employed during magnetic resonance imaging owe their advantage over their dual counterparts to the fact that they do not involve any quenching caused by interference between the two modes. The chemistry involving oxides of manganese is highly significant due to their applicability as MRI contrast agents. Manganese oxides are usually known to display a dominant T 1 relaxation enhancement. But, in this work, an engineered structure of manganese oxide (Mn 2 O 3) nanoparticles encapsulated within mesoporous carbon frameworks was developed which exhibited dominant T 2 contrast enhancement, through regulation of contact between the magnetic ion and water. Microstructural characterization revealed that the mesoporous carbon frameworks were spherical in shape and the nanoparticles within them had an average size of 40–50 nm. Relaxivity measurement, MRI experiments and cell viability assay convincingly established the system as a new class of biocompatible T 2 based magnetic resonance imaging agent. Image 1 • Mn 2 O 3 nanoparticles encapsulated by mesoporous carbon framework were developed. • Regulated contact between Mn3+ ion and water annihilates T 1 relaxation. • The developed nanosystem shows exclusive T 2 contrast. • Cell viability assay established suitability of the system for biomedical purpose. [ABSTRACT FROM AUTHOR]

The accuracy of magnetic resonance imaging (MRI) scanning can be improved using a multifunctional nanosystem having T1–T2 dual contrast enhancement. Specifically, the combination of both T1 and T2 effects in a single system helps in acquiring cross validated information during dual mode MRI and reduces the required dose. In this study, polyethylene glycol (PEG) stabilized MnFe2O4@MnO Janus nanoparticles were developed as novel dual-mode MR imaging agents. MnO contributed to T1 contrast whereas MnFe2O4 enabled T2 contrast. The PEG molecules afforded solubility and stability to the contrast agent in water, making it acceptable for biomedical purposes. The biocompatibility of the developed nanosystem was confirmed by cell viability studies. The r2/r1 ratio remained at a suitable value, justifying the applicability of the contrast agent for dual mode MRI. Finally, the efficiency of the agent for T1–T2 contrast enhancement was confirmed through in vitro and ex vivo MRI experiments. [ABSTRACT FROM AUTHOR]

Magnetic resonance imaging (MRI) is one of the widely used medical diagnostic techniques due to its non-invasive nature, higher resolution and efficiency in soft tissue imaging. MRI contrast agents with high relaxivity and biocompatibility are of great importance for successful clinical diagnosis. Manganese based substances have emerged as new class of MR imaging agents due to their impressive contrast ability. In this study, we have reported development of manganese oxide (Mn 3 O 4 ) nanoparticles encapsulated in mesoporous 3D carbon framework (CF) functionalized by polyethylene glycol (PEG) as T 1 based MRI contrast agent. PEG functionalization endowed solubility and stability of the contrast agent in water which are highly essential traits of MRI contrast agents. The carbon framework provided excellent biocompatibility by ruling out possibility of metal ion exposure (offering suitability for in vivo application) and simultaneously enabled water exchange through its pores which led to T 1 contrast improvement. The as-prepared PEG modified manganese oxide@CF nanosystem exhibited paramagnetic behaviour at room temperature, enhanced water proton relaxation and facilitated contrast of T 1 -weighted MR images. [ABSTRACT FROM AUTHOR]

In this paper, we present a detailed study of temperature-based ion implantation of phosphorus dopants in Ge for varying dose and anneal conditions through fabricated n+/p junctions and n-type MOSFETs (nMOSFETs). In comparison with room temperature (RT) (25 °C) and hot (400 °C) implantation, cryogenic (−100 °C) implantation with a dose of 2.2e15 \mathrmcm^-2 followed by a (400 °C) rapid thermal annealing leads to 1) lower junction leakage with higher activation energy and 2) lower sheet resistance with higher dopant activation and shallower junction depth. Gate-last Ge nMOSFETs fabricated using cryogenic implanted n+/p source/drain junction (2.2e15 \mathrmcm^-2 ) exhibit lower off-current (upto $5\times )$ and higher ON-current compared with RT (25 °C) and hot (400 °C) implanted nMOSFETs. This paper demonstrates that cryogenic implantation (−100 °C) can enable high-performance Ge nMOSFETs by alleviating the problems of lower activation and high diffusion of phosphorus in Ge. [ABSTRACT FROM PUBLISHER]

Abstract: The present investigation deals with designing of savlon loaded blend hydrogels (termed cryogels) of polyvinyl alcohol (PVA) and alginate by repeated freeze–thaw method and their characterization by SEM and FTIR techniques. The FTIR spectra clearly reveal that savlon loaded alginate and PVA blends are bonded together through hydrogen bonding. The SEM analysis suggests that cryogels show a well defined porous morphology. The prepared cryogels were also investigated for swelling and deswelling behaviors. The results reveal that both the swelling and deswelling processes greatly depend on the chemical composition of the cryogels, number of freeze–thaw cycles and pH and temperature of the swelling bath. The savlon loaded blends were also investigated for their in vitro blood compatibility and antibacterial activity. [ABSTRACT FROM AUTHOR]