Browsing by Author "Hernandez, Francisco C. Robles"
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Item High-K dielectric sulfur-selenium alloys(AAAS, 2019) Susarla, Sandhya; Tsafack, Thierry; Owuor, Peter Samora; Puthirath, Anand B.; Hachtel, Jordan A.; Babu, Ganguli; Apte, Amey; Jawdat, BenMaan I.; Hilario, Martin S.; Lerma, Albert; Calderon, Hector A.; Hernandez, Francisco C. Robles; Tam, David W.; Li, Tong; Lupini, Andrew R.; Idrobo, Juan Carlos; Lou, Jun; Wei, Bingqing; Dai, Pengcheng; Tiwary, Chandra Sekhar; Ajayan, Pulickel M.Upcoming advancements in flexible technology require mechanically compliant dielectric materials. Current dielectrics have either high dielectric constant, K (e.g., metal oxides) or good flexibility (e.g., polymers). Here, we achieve a golden mean of these properties and obtain a lightweight, viscoelastic, high-K dielectric material by combining two nonpolar, brittle constituents, namely, sulfur (S) and selenium (Se). This S-Se alloy retains polymer-like mechanical flexibility along with a dielectric strength (40 kV/mm) and a high dielectric constant (K = 74 at 1 MHz) similar to those of established metal oxides. Our theoretical model suggests that the principal reason is the strong dipole moment generated due to the unique structural orientation between S and Se atoms. The S-Se alloys can bridge the chasm between mechanically soft and high-K dielectric materials toward several flexible device applications.Item Substitution of copper atoms into defect-rich molybdenum sulfides and their electrocatalytic activity(Royal Society of Chemistry, 2021) Wang, Zixing; Kannan, Harikishan; Su, Tonghui; Swaminathan, Jayashree; Shirodkar, Sharmila N.; Hernandez, Francisco C. Robles; Benavides, Hector Calderon; Vajtai, Robert; Yakobson, Boris I.; Meiyazhagan, Ashokkumar; Ajayan, Pulickel M.Studies on intercalation or substitution of atoms into layered two-dimensional (2D) materials are rapidly expanding and gaining significant consideration due to their importance in electronics, catalysts, batteries, sensors, etc. In this manuscript, we report a straightforward method to create sulphur (S) deficient molybdenum (Mo) sulfide (MoS2−x) structures and substitute them with zerovalent copper (Cu) atoms using a colloidal synthesis method. The synthesized materials were studied using several techniques to understand the proportion and position of copper atoms and the effect of copper functionalization. Specifically, the impact of change in the ratio of Cu : S and the hydrogen evolution reaction (HER) activity of the derived materials were evaluated. This technique paves the way for the synthesis of various functionalized 2D materials with a significant impact on their physical and chemical behavior making them potential candidates for catalysis and several other applications such as energy storage and the development of numerous functional devices.