A novel preparation method of B-doped p-type BaSi2 (p-BaSi2) is proposed to realize heterojunction crystalline Si solar cells with p-BaSi2. The method consists of thermal evaporation of BaSi2 on B-doped amorphous Si (a-Si). In this study, the effect of a-Si interlayers and substrate temperature during BaSi2 evaporation on the electrical characteristics and crystalline quality of the evaporated films were investigated. While no cracks were found in the BaSi2 films formed using hydrogenated a-Si deposited by plasma enhanced chemical vapor deposition (PECVD), the films formed with sputtered a-Si have cracks. In addition, BaSi2 films formed with a 600 °C substrate temperature using PECVD a-Si showed p-type characteristics. After a post-deposition anneal at 800 °C for 5 minutes, the film hole density was measured at 1.3×1019 cm-3 and boron was found to be uniformly distributed throughout the film. These results show that the proposed method using PECVD is promising to obtain p-BaSi2 thin films with high hole density for p-BaSi2/n-type crystalline Si heterojunction solar cells.

Understanding the structural evolution of electrode material during electrochemical activity is important to elucidate the mechanism of (de)lithiation, and improve the electrochemical function based on the material properties. In this study, lithium vanadium oxide (LVO, LiV3O8) was investigated using ex-situ, in-situ, and operando experiments. Via a combination of in-situ X-ray diffraction (XRD) and density functional theory results, a reversible structural evolution during lithiation was revealed: from Li poor α phase (LiV3O8) to Li rich α phase (Li2.5V3O8) and finally β phase (Li4V3O8). In-situ and operando energy dispersive X-ray diffraction (EDXRD) provided tomographic information to visualize the spatial location of the phase evolution within the LVO electrode while inside a sealed lithium ion battery.

There is growing interest in reducing the use of ordinary Portland cement (OPC) owing to its high energy consumption and CO2 emissions. An environmentally-friendly alternative is the use of geopolymers, which can potentially reduce direct CO2 emissions through the appropriate choice of raw materials, mix design, and curing regimes. In this regard geopolymer mortars are also realistic candidates for the replacement of OPC mortars in nuclear waste immobilisation applications as they provide a more durable incorporation matrix as well as suppressing the formation of radiolytic hydrogen. The advantages of geopolymers over OPC for nuclear waste immobilisation include i) lower water content as alkaline activator is the main component that drives geopolymerisation, ii) higher thermal stability (<600°-800°C) compared to OPC concrete (<300°C), iii) higher compressive strength (50-80 MPa), and iv) lower leachability of radioactive ions when the mix design and curing temperature are appropriately balanced. UNSW and ANSTO have embarked on a long-term research program to investigate the possibility of using geopolymers for the immobilisation of Intermediate Level Liquid Waste (ILLW), the focus of which will be around the influence of gamma-irradiation on the durability.

Analysis of the total surface energy γT and its three components as established by the van Oss-Chaudhury-Good Theory (vOCG) is conducted via Three Liquid Contact Angle Analysis (3LCAA). γT is correlated with the composition of the top monolayers (ML) obtained from High-Resolution Ion Beam Analysis (HR-IBA). Control of γT enables surface engineering for wafer bonding (Nano-BondingTM) and/or epitaxial growth. Native oxides on boron-doped p-Si(100) are found to average γT of 53 ± 1.4 mJ/m2) and are always hydrophilic. An HF in methanol or aqueous HF etch for 60 s always renders Si(100) hydrophobic. Its γT decreases by 20% to 44 ± 3 mJ/m2 in HF in methanol etch and by 10% to 48 ± 3 mJ/m2 in aqueous HF. On the contrary, GaAs(100) native oxides are found to always be hydrophobic. Tellurium n+-doped GaAs(100) yields an average of γT of 37 ± 2 mJ/m2, 96% of which is due to the Lifshitz-Van der Waals molecular interactions (γLW = 36 ± 1 mJ/m2). However, hydrophobic GaAs(100) can be made highly hydrophilic. After etching, γT increases by almost 50% to 66 ± 1.4 mJ/m2. 3LCAA shows that the γT increase is due to electron acceptor and donor interactions, while the Lifshitz-van der Waals energy γLW remains constant. IBA combining the 3.039 ± 0.01 MeV oxygen nuclear resonance with <111> channeling, shows that oxygen on Si(100) decreases by 10% after aqueous HF etching, from 13.3 ± 0.3 monolayers (ML) to 11.8 ± 0.4 ML 1 hour after etch.Te-doped GaAs(100) exhibits consistent oxygen coverage of 7.2 ± 1.4 ML, decreasing by 50% after etching to a highly hydrophilic surface with 3.6 ± 0.2 oxygen ML. IBA shows that etching does not modify the GaAs surface stoichiometry to within 1% . Combining 3LCAA with HR-IBA provides a quantitative metrology to measure how GaAs and Si surfaces can be altered to a different hydroaffinity and surface termination.

Metallic silver nanoparticles were synthesized using a hydrothermal route for use in high throughput biosensing applications. Particle shape was engineered by varying polyvinyl pyrollidone (PVP) concentration in the precursor mixture, resulting in the emergence of flat triangular shaped nanoparticles with increasing PVP content. The hydrothermal method was found to yield particles with better particle size distribution and longer shelf life relative to polyol synthesis particles.

Characterization of three vendor’s bulk semi-insulating GaN:Fe wafers, grown by either hydride vapor phase epitaxy or the ammonothermal method, was performed using: scanning electron microscopy, secondary ion mass spectroscopy, high resolution X-ray diffraction, cathodoluminescence, photoluminescence, and high voltage testing. Although the Fe doping level is significantly different for each growth method, both are promising for the fabrication of PCSS devices operating in the lock-on mode.

Graphene nanosheets were prepared by pulsed Nd:YAG laser ablation of graphite target in H2O under ambient conditions. The synthesized graphene nanosheets were characterized by high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), Raman spectroscopy and Selected Area Electron Diffraction (SAED). The obtained structural and morphological analysis confirmed that the graphene nanosheets could be formed in an aqueous medium via one step method where a nanosecond pulsed near-infrared (NIR) laser (λ = 1064 nm) is used to ablate the surface of a pure graphite target. Compared to other used chemical methods to synthesis graphene nanosheets, laser ablation is an easy, versatile, environmental friendly and rapidly growing method for the synthesis of nanostructured materials such as graphene nanosheets. This technique showed normal operation in liquid medium (i.e. water or organic) under ambient conditions. Our study confirmed the great potential of laser ablation in liquid method for the fabrication of graphene nanosheets based nanofluids wich has a potential applicatiuon as a heat transfer fluid.

Low-density, highly porous graphene/graphene oxide (GO) based-foams have shown high performance in energy absorption applications, even under high compressive deformations. In general, foams are very effective as energy dissipative materials and have been widely used in many areas such as automotive, aerospace and biomedical industries. In the case of graphene-based foams, the good mechanical properties are mainly attributed to the intrinsic graphene and/or GO electronic and mechanical properties. Despite the attractive physical properties of graphene/GO based-foams, their structural and thermal stabilities are still a problem for some applications. For instance, they are easily degraded when placed in flowing solutions, either by the collapsing of their layers or just by structural disintegration into small pieces. Recently, a new and scalable synthetic approach to produce low-density 3D macroscopic GO structure interconnected with polydimethylsiloxane (PDMS) polymeric chains (pGO) was proposed. A controlled amount of PDMS is infused into the freeze-dried foam resulting into a very rigid structure with improved mechanical properties, such as tensile plasticity and toughness. The PDMS wets the graphene oxide sheets and acts like a glue bonding PDMS and GO sheets. In order to obtain further insights on mechanisms behind the enhanced mechanical pGO response we carried out fully atomistic molecular dynamics (MD) simulations. Based on MD results, we build up a structural model that can explain the experimentally observed mechanical behavior.

Thermocapillary dewetting of liquids and molten films has recently emerged as a viable alternative to conventional microprocessing methods. As this thermal gradient-induced mechanism is universal, it can be applied to any material. This work explores the sequential dewetting of materials with varying melting points, including polymers and metals, to create aligned morphologies. The variation in melting point allows for the dewetting of single layers at a time or mobility-limited simultaneous dewetting. As a result, a variety of multimaterial structures can be produced with built-in alignment, such as arrays of concentric circles, lines with periodic segmentation, or islands on holes. This approach employs photothermal methods to induce the necessary thermal gradient, manipulating several variables in order to influence the consequent structures. Adjusting laser power and light intensity allows for the control of temperature for selective dewetting of films; altering beam size and exposure time affects the extent of dewetting in terms of diameter size; overlap effects and simultaneous dewetting can result in complex architectures. This controlled writing of patterns also presents a technique to create both masks at low temperatures for conductive multilayers as well as templates for electrospray deposition.

This work reports the synthesis of undoped and alkali metal doped thermochromic vanadium dioxide thin films by sol-gel spin coating and subsequent low-temperature annealing at 450 °C in N2-H2 atmosphere. The effect of sodium and potassium on the phase transition temperature as well as on the solar modulations were investigated. A dopant concentration of 0.3 at% resulted in a reduction of the critical transition temperature (Tc) from 62 °C to 57 °C and 47 °C for the sodium and potassium doped films, respectively. Moreover, both dopants improved the solar modulations (ΔTsol) of the undoped VO2 films from 3.81 to 9.44 and 5.43 %, respectively.

The generation of filaments constituted by nanocomposites allows printing pieces with functional properties. A method is proposed for incorporating nanoparticles in plastic filaments (thermoplastic polyurethane, PU) by diffusion in the swollen material. The nanoparticles must be dispersed in solvents (or solvent mixtures) in which the polymer swells but does not dissolve. Nanoparticles are incorporated mainly at the surface as revealed by SEM/EDS mapping. The thermal properties (studied by DSC and TGA) of the PU are only slightly affected by the presence of NPs. Test pieces successfully are printed using the modified filaments. Incorporation of solid lubricant (MoS2) nanoparticles decreases the coefficient of friction of the printed test samples.

A complex mechanism of interfacial oxygen scavenging is revealed by electron energy-loss spectroscopy (EELS) for a resistive switching oxide of SrTiO3 with a scavenging layer of Ta. When Ta thin layer is inserted at one of the interfaces of Pt/SrTiO3/Pt structure, a large reduction of electrical resistance is induced for the structure, and oxygen defects are introduced at the interfacial part of SrTiO3. In the resistance decrease by voltage applications, simultaneous occurrence of oxidation and reduction of Ta scavenging layer is shown by EELS analyses from the low-loss spectra. The EELS and scanning transmission electron microscopy observations demonstrate that oxygen scavenging by Ta layer is an interfacial phenomenon where the redox reactions occur at the whole part of the interface. In addition, Pt electrode of the structure, which is chemically inert for oxidation, is revealed to have significant effects in the scavenging processes.

GeTe/Sb2Te3 superlattices, also known as interfacial phase-change memory (iPCM), exhibit significantly faster switching and are characterized by much lower power consumption and longer data retention compared to devices based on alloyed materials. In early work, the superior performance of iPCM was linked to a crystal-crystal transition between the SET and RESET states. As the primary mechanism, a change in the stacking order of Ge and Te planes within a GeTe block was suggested. Subsequent STEM studies on epitaxial GeTe/Sb2Te3 superlattices demonstrated that the GeTe blocks were not located between Sb2Te3 quintuple layers but, were incorporated inside the latter, providing a serious challenge to the early explanation. In this work, we demonstrate that changes associated with the reconstruction of the SbTe terminating layers nearest to van der Waals gap leads to a pronounced change in the density of states and can serve as an alternative explanation for a large property contrast between the SET and RESET states in GeTe/Sb2Te3 superlattices.