Structure and optical properties of 2D layered MoS2 crystals implemented with novel friction induced crystal growth

Abstract

We used X-ray diffraction, and Raman and photoluminescence (PL) spectroscopies to examine the structure and optical properties of molybdenum disulfide (MoS2) crystals grown by friction at the interface between two materials. MoS2 is produced chemically from molybdenum dithiocarbamates (MoDTC) in synthetic oil under sliding friction conditions. The X-ray diffraction (XRD) patterns indicate that the structure of the MoS2 is layered with the c-axis perpendicular to the surface. The MoS2 layer was formed on stainless steel and germanium by friction at the interface between these materials and high carbon chromium bearing steel. The number of layers is estimated to be N (N > 6) from the distance between the Raman frequencies of the E12g and A1g modes. For MoS2 grown on stainless steel, exciton peak is observed in the PL spectrum at room temperature. These results show that this friction induced crystal growth method is viable for synthesizing atomic layers of MoS2 at solid surfaces.

NbTe4 Phase‐Change Material: Breaking the Phase‐Change Temperature Balance in 2D Van der Waals Transition‐Metal Binary Chalcogenide

“…[5] Among these compounds, MoTe 2 exhibits polymorphic phase transitions within hexagonal (2H) and monoclinic (1T′) or orthorhombic (T d ) crystal structures; switching between these phases can also be realized by the application of external stimuli such as temperature, electric-field or pressure. [3,[6][7][8][9][10][11] As a result, MoTe 2 has been extensively studied as a switching layer in nextgeneration non-volatile memories (NVMs), such as resistive random access memory (ReRAM) and phase-change random access memory (PCRAM), due to the large changes in electrical properties ranging from metallic to semiconducting accessable by switching between phases. Zhang et al reported an electric-field-induced structural transition from a 2H semiconducting to a distorted transient [11,15,[29][30][31] the T c and T m values of NbTe 4 were defined by the onset temperature of crystallization and melting peaks in this study; B) XRD curves of NbTe 4 thin films annealed at various temperatures; C) cross-sectional TEM image of 350 °C annealed NbTe 4 thin film; D) zoomed in image of the white-box area in (C); E) the FFT pattern taken from the area of (D).…”

“…[ 5 ] Among these compounds, MoTe 2 exhibits polymorphic phase transitions within hexagonal (2H) and monoclinic (1T′) or orthorhombic ( T d ) crystal structures; switching between these phases can also be realized by the application of external stimuli such as temperature, electric‐field or pressure. [ 3,6–11 ] As a result, MoTe 2 has been extensively studied as a switching layer in next‐generation non‐volatile memories (NVMs), such as resistive random access memory (ReRAM) and phase‐change random access memory (PCRAM), due to the large changes in electrical properties ranging from metallic to semiconducting accessable by switching between phases. Zhang et al.…”

Structural characterisation of iron sulfide tribofilms formed on carbon and stainless steels

“…In particular, MoDTC reduces friction by forming a MoS 2 tribofilm on the contact area, [7][8][9][10] whereas ZDDP prevents wear by forming an amorphous tribofilm with multilayered structures. 5,6,11 Thus, recent studies have focused on the influence of metallic and nonmetallic substrates in the tribochemical reactions of MoDTC [12][13][14] and ZDDP. [15][16][17] Chlorine-containing EP additives are commonly used in the cold-working processes of steel because of their cost effectiveness and high lubricity along with high corrosion resistance.…”

“…In particular, MoDTC reduces friction by forming a MoS 2 tribofilm on the contact area, 7–10 whereas ZDDP prevents wear by forming an amorphous tribofilm with multilayered structures 5,6,11 . Thus, recent studies have focused on the influence of metallic and nonmetallic substrates in the tribochemical reactions of MoDTC 12–14 and ZDDP 15–17 …”

“…This study investigated the structures of tribofilms formed by polysulfide on carbon steel and stainless steel using four ex situ techniques: XPS, 7,10,16,22,31 Raman spectroscopy, 8,9,12–14,23,24,32–35 X‐ray diffraction (XRD) analysis, 12,13,36–41 and transmission electron microscopy (TEM) 7,11,14–16 to understand the causes of susceptibility to scuffing in carbon steel and stainless steel by the multifaceted structural analysis of the tribofilms.…”