title: Growth evolution and phase transition from chalcocite to digenite in nanocrystalline copper sulfide: Morphological, optical and electrical properties.
abstract: Copper sulfide is a promising p-type inorganic semiconductor for optoelectronic devices such as solar cells, due its small band gap energy and its electrical properties. In this work nanocrystalline copper sulfide (Cu x S), with two stoichiometric ratios (x = 2, 1.8) was obtained by one-pot synthesis at 220, 230, 240 and 260 °C in an organic solvent and amorphous Cu x S was obtained in aqueous solution. Nanoparticle-like nucleation centers are formed at lower temperatures (220 °C), mixtures of morphologies (nanorods, nanodisks and nanoprisms) are seen at 230 and 240 °C, in which the nanodisks are predominant, while big hexagonal/prismatic crystals are obtained at 260 °C according to TEM results. A mixture of chalcocite and digenite phases was found at 230 and 240 °C, while a clear transition to a pure digenite phase was seen at 260 °C. The evolution of morphology and transition of phases is consistent to the electrical, optical, and morphological properties of the copper sulfide. In fact, digenite Cu1.8S is less resistive (346 Ω/sq) and has a lower energy band gap (1.6 eV) than chalcocite Cu2S (5.72 × 10(5) Ω/sq, 1.87 eV). Low resistivity was also obtained in Cu x S synthesized in aqueous solution, despite its amorphous structure. All Cu x S products could be promising for optoelectronic applications.
authors.affiliation: Posgrado en Ciencia e Ingeniería de Materiales, Centro de Física Aplicada y Tecnología Avanzada, Universidad Nacional Autónoma de México, 76230, Querétaro, México.
authors.forename: Priscilla Vasthi
authors.initials: PV
authors.lastname: Quintana-Ramirez
authors.affiliation: Escuela Nacional de Estudios Superiores Unidad León, UNAM, Boulevard UNAM No. 2011 Predio el Saucillo y el Potrero, 36969, León Guanajuato, México.
authors.forename: Ma Concepción
authors.initials: MC
authors.lastname: Arenas-Arrocena
authors.affiliation: Facultad de Química, Materiales Universidad Autónoma de Querétaro, 76010, Querétaro, México.
authors.forename: José
authors.initials: J
authors.lastname: Santos-Cruz
authors.affiliation: Centro de Geociencias, UNAM, 76230, Querétaro, México.
authors.forename: Marina
authors.initials: M
authors.lastname: Vega-González
authors.affiliation: Departamento de Ingeniería en Energía, Universidad Politécnica de Guanajuato, 38483, Guanajuato, México.
authors.forename: Omar
authors.initials: O
authors.lastname: Martínez-Alvarez
authors.affiliation: Departamento de Ingeniería Molecular de Materiales, CFATA, UNAM, 76230, Querétaro, México.
authors.forename: Víctor Manuel
authors.initials: VM
authors.lastname: Castaño-Meneses
authors.affiliation: Escuela Nacional de Estudios Superiores Unidad León, UNAM, Boulevard UNAM No. 2011 Predio el Saucillo y el Potrero, 36969, León Guanajuato, México.
authors.forename: Laura Susana
authors.initials: LS
authors.lastname: Acosta-Torres
authors.affiliation: Escuela Nacional de Estudios Superiores Unidad León, UNAM, Boulevard UNAM No. 2011 Predio el Saucillo y el Potrero, 36969, León Guanajuato, México.
authors.forename: Javier
authors.initials: J
authors.lastname: de la Fuente-Hernández
keywords: abundant materials in the crust of Earth; electrical resistance; nanocrystals; nanodisks; non-toxic semiconductors; optical band gap; phase transition; photocurrent