Gallium sulfide (GaS x ) was synthesized for the first time via atomic layer deposition (ALD), using hexakis(dimethylamido)digallium and hydrogen sulfide. The growth characteristics and surface reaction mechanism for the GaS x ALD were investigated using in situ quartz crystal microbalance, quadrupole mass spectrometry, and Fourier transform infrared spectroscopy measurements. The as-deposited films were analyzed for their surface morphology, elemental stoichiometry, chemical states and stability, and crystallinity, using a variety of characterization techniques. These measurements revealed that the GaS x growth was self-limiting in the temperature range of 125–225 °C and the growth per cycle decreased linearly with increasing temperature, from ∼1.0 Å/cycle at 125 °C to ∼0.5 Å/cycle at 225 °C. The S/Ga ratio was between 1.0 and 1.2 in the temperature range of 125–200 °C, but decreased to 0.75 at 225 °C. The GaS x films were amorphous and the refractive index increased from ∼1.8 to 2.5 with increasing temperature. Significantly, electrochemical testing showed that the ALD GaS x is a promising lithium-ion battery (LIB) anode material, exhibiting reliable cyclability and a high specific capacity of 770 mAh/g at a current density of 320 mA/g in the voltage window of 0.01–2.00 V.

Molybdenum disulfide (MoS2) has a wide range of applications from electronics to catalysis. While the properties of single-layer and multilayer MoS2 films are well understood, controlling the deposited MoS2 polytype remains a significant challenge. In this work, we employ chemical bath deposition, an aqueous deposition technique, to deposit large area MoS2 thin films at room temperature. Using Raman spectroscopy and x-ray photoelectron spectroscopy, we show that the deposited MoS2 polytype can be changed from semiconducting 2H MoS2 on hydrophobic –CH3 and –CO2C6F5 terminated self-assembled monolayers (SAMs) to semimetallic 1T MoS2 on hydrophilic –OH and –COOH terminated SAMs. The data suggest that the deposition of MoS2 polytypes is controlled by the substrate surface energy. High surface energy substrates stabilize 1T MoS2 films, while 2H MoS2 is deposited on lower surface energy substrates. This effect appears to be general enabling the deposition of different MoS2 polytypes on a wide range of substrates.

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Single crystals of Pr2Fe(4-x)Co(x)Sb5 (1 < x < 2.5) were grown from a Bi flux and characterized by X-ray diffraction. The compounds adopt the La2Fe4Sb5 structure type (I4/mmm). The structure of Pr2Fe(4-x)Co(x)Sb5 (1 < x < 2.5) contains a network of transition metals forming isosceles triangles. The x ∼ 1 analogue is metallic and exhibits a magnetic transition at T1 ≈ 25 K. The magnetic moment obtained from the Curie-Weiss fit is 11.49(4) μ(B), which is larger than the spin-only Pr(3+) moment. The x ∼ 2 analogue orders magnetically at T1 ≈ 80 and T2 ≈ 45 K. This is the first case of the substitution of Co into the La2Fe4Sb5 structure type, evidenced by the increased concentration of dopant with decreased lattice parameters coupled with a change in the transition temperature with a change in the cobalt concentration. The added complexity in the magnetic behavior of the x ∼ 1 and 2 analogues indicates that the increased concentration of Co invokes an additional magnetic contribution of the transition metal in the sublattice. Furthermore, X-ray photoelectron spectroscopy measurements support the change in the oxidation states of transition metals with increasing cobalt concentration.

Molybdenum disulfide (MoS 2 ) is a transition-metal dichalcogenide with many applications including in electronic devices and sensors. A critical issue in the development of these devices is the high resistance between the metal contact and the molybdenum disulfide layer. In this study, we employ Raman spectroscopy and X-ray photoelectron spectroscopy to investigate the modification of Au−MoS 2 contact properties using functionalized alkanethiolate self-assembled monolayers (SAMs). We demonstrate that both 2H and 1T MoS 2 strongly interact with the underlying Au substrate. The electronic properties of the interface are mediated by the dipole moment of the alkanethiolate SAM, which have a −CH 3 , −CO 2 C 6 F 5 , −OH, or −COOH terminal group. Finally, we demonstrate the site-selective deposition of 2H and 1T MoS 2 on micropatterned SAMs to form conducting−semiconducting patterned MoS 2 films.