Magnetic Properties of Semiconducting Spinel CdCr₂S₄ Nanostructured Films Grown by Low-Pressure Metal–Organic Chemical Vapor Deposition

Abstract

Magnetic semiconductors are being extensively investigated because of their promise to provide new functionalities and device concepts for spintronic applications. Nevertheless, it remains a challenge to obtain high-quality thin films of these materials for device usage, particularly of chalcogenide-based magnetic semiconductors. The chalcogenide spinel CdCr 2 S 4 is a well-established ferromagnetic semiconductor. In bulk form, it exhibits unique properties such as colossal magnetocapacitance and magnetoresistance effects and is a promising candidate for spintronic applications. Because of its semiconducting properties and band gap in the visible wavelength range, CdCr 2 S 4 offers exciting possibilities for tailoring its optical and magnetic properties. However, applications that utilize its unique combination of optical, electrical, and magnetic properties are limited because of difficulties in growing high-quality films. Herein, we demonstrate a simple low-pressure metal−organic chemical vapor deposition (MOCVD) method for growth of high-quality nanostructured CdCr 2 S 4 thin films using metal−organic precursors of Cd and Cr, which provides an attractive route for scaling to large areas. The deposited films are uniform with excellent phase purity, morphology, and crystallinity. In addition to structural and optical characterization, the static and dynamic magnetic properties of the MOCVD grown films have been investigated in detail.

Dithiocarbamate Complexes as Single Source Precursors to Nanoscale Binary, Ternary and Quaternary Metal Sulfides

“…Gupta and co-workers recently reported the vaporization of mixtures of [Cd-(S 2 CNEt 2 ) 2 ] and [Cr(S 2 CNEt 2 ) 3 ] with elemental sulfur, resulting in deposition of thin films of CdCr 2 S 4 onto borosilicate glass at 500 °C. 598 These were optimized conditions, and decreasing the temperature led to sulfurdeficient materials, while under other conditions, deposition of CdS (wurtzite) dominated. Film thickness can be controlled, allowing films of between 300 and 600 nm thickness and with grain sizes of 100−200 nm, and their optical and magnetic properties have been systematically investigated.…”

“…A number of other ternary sulfides have been prepared using the DTC approach, including (Ni,Co) 3 S 4 , , CdCr 2 S 4 , MIn 2 S 4 (M = Mn, Fe, Co), and In 4 SnS 8 . Nickel–cobalt sulfides have several phases including NiCo 8 S 8 (pentlandite structure), NiCo 2 S 4 /CoNi 2 S 4 (thiospinels).…”

“…Spinel, CdCr 2 S 4 , is a ferromagnetic semiconductor, with interesting physical properties such as colossal magnetocapacitance and magnetoresistance effects, while with a band gap in the visible range, it presents opportunities for tailoring its optical and magnetic properties. Gupta and co-workers recently reported the vaporization of mixtures of [Cd­(S 2 CNEt 2 ) 2 ] and [Cr­(S 2 CNEt 2 ) 3 ] with elemental sulfur, resulting in deposition of thin films of CdCr 2 S 4 onto borosilicate glass at 500 °C . These were optimized conditions, and decreasing the temperature led to sulfur-deficient materials, while under other conditions, deposition of CdS (wurtzite) dominated.…”

Novel Strategy toward Chromium-Based Thiospinel Multifunctional Magnetic Materials from Amorphous Chromites

“…It is particularly worth mentioning that Gupta’s group has achieved a large number of remarkable results concerning the synthesis, properties, and applications of Cr-based chalcospinel nanomaterials. Based on wet chemical colloidal synthesis technology, they have successfully obtained a series of phase-pure Cr-based chalcospinel nanocrystals, − which greatly contributed to the development of this material system. Meanwhile, some other synthesis techniques, including the microwave-assisted polyol method, − mechanical alloying, − thermal decomposition, solvothermal reactions, and sonochemical synthesis, have also been successfully applied to the preparation of Cr-based chalcospinels.…”