Ag nanoparticle decorated molybdenum oxide structures: growth, characterization, DFT studies and their application to enhanced field emission

Reversible, stable Li-ion storage in 2 D single crystal orthorhombic α-MoO3 anodes

Engineering two dimensional (2D) materials at atomic level is a key factor to achieve enhanced electrochemical Li-ion storage properties. This work demonstrates that single crystals of orthorhombic α-MoO₃ phase can preferentially grow with a 2D nanoarchitecture via a ball-milling process, followed by heat treatment at elevated temperature. Detailed FE-SEM and TEM micrographs proved the 2D architecture of α-MoO₃ nanoparticles and Raman spectroscopy evidenced the active vibration modes that correspond to the orthorhombic α-MoO₃ phase. Single crystalline MoO₃ belts depicted high intensity of (0 2 0) and (0 4 0) indexed planes indicating a preferential arrangement. As Li-ion host anode, the 2D α-MoO₃ nanostructure delivered high reversible specific discharge capacity of ~540 mA h g^-1 at 0.2 C-rate with 99.9% coulombic efficiency as well as 63% capacity retention after 200 charge-discharge cycles. An excellent reversible Li-ion storage performance (high capacity, longer cycle life and good rate capability) was attributed to the 2D α-MoO₃ arrangement consists of MoO₆ octahedron by corner sharing chains.

Growth of Molybdenum Trioxide Nanoribbons on Oriented Ag and Au Nanostructures: A Scanning Electron Microscopy (SEM) Study

We report the growth of molybdenum trioxide (MoO3) nanoribbons (NRs) on epitaxial Ag and oriented Au nanostructures (NSs) using an ultra-high vacuum (UHV)-molecular beam epitaxy (MBE) technique at different substrate temperatures. An approximately 2 nm silver (Ag) film has been deposited at different growth temperatures (using UHV-MBE) on cleaned Si(100), Si(110), and Si(111) substrates. For faceted Au NSs, an approximately 50 nm Au film has been deposited (using high-vacuum thermal evaporation) on a Si(100) substrate with a native oxide layer at the interface and the sample was annealed in low vacuum (≈10-2) and at high temperature (≈975°C). Scanning electron microscopy measurements were performed to determine the morphology of MoO3/Ag and MoO3/Au composite films. From energy dispersive X-ray spectroscopy elemental mapping and line scans it is found that faceted Au NSs are more favorable for the growth of MoO3 NRs than epitaxial Ag microstructures.

P-type β-MoO2 nanostructures on n-Si by hydrogenation process: synthesis and application towards self-biased UV-visible photodetection

We report on the synthesis and UV-vis photodetection application of p-type MoO₂ nanostructures (NSs) on Si substrate. β-MoO₂ NSs have been synthesized from previously grown α-MoO₃ structures/n-type Si via a hydrogenation process at 450 °C. After hydrogenation, the α-MoO₃ structures were completely converted into β-MoO₂ NSs without the presence of sub-oxidized phases of molybdenum oxide. The as-grown NSs exhibited very good p-type electrical conductivity of ≈2.02 × 10³ S-cm^-1 with hole mobility of ≈7.8 ± 1.3 cm²-V^-1-Sec^-1. To explore optoelectronic properties of p-type β-MoO₂ NSs, we have fabricated a p-MoO₂/n-Si heterojunction photodetector device with Au as the top and Al as the bottom contacts. The device exhibits peak photoresponsivity of ≈0.155 A W^-1 with maximum detectivity ≈1.28 × 10¹¹ cm-Hz^1/2-W^-1 and 44% external quantum efficiency around ≈436 nm, following the highest photoresponse (I _ph/I _d ≈ 6.4 × 10²) and good response speed (rise time ∼29 ms and decay time ∼38 ms) at -1.5 V. Importantly, this device also shows good self-powered high-speed (rise time ∼47 ms and decay time ∼70 ms) photodetection performance with peak responsivity and detectivity of ≈45 mA W^-1 and ≈4.05 × 10¹⁰ cm-Hz^1/2-W^-1, respectively. This broadband UV-visible light detection feature can be attributed to the coordinated effects of MoO₂ band-edge absorption, interfacial defects and self absorption in Si. The photodetection behavior of the device has been understood by proposed energy-band diagrams with the help of an experimentally derived work function, band gap and valence band maximum position of MoO₂ NSs.