Chemical Instability of an Interface between Silver and Bi₂Se₃ Topological Insulator at Room Temperature

Abstract

Understanding an interaction at an interface between a topological insulator and a metal is of critical importance when designing electronic and spintronic devices or when such systems are used in catalysis. In this paper, we report on a chemical instability of the interface between Bi 2 Se 3 and Ag studied by X-ray powder diffraction and electron microscopy. We present strong experimental evidence of a redox solid-state reaction occurring at the interface with kinetics that is significant already at room temperature. The reaction yields Ag 2 Se, AgBiSe 2 , and Bi. The unexpected room-temperature chemical instability of the interface should be considered for all future theoretical and applicative studies involving the interface between Bi 2 Se 3 and Ag.

Growth, morphology and stability of Au in contact with the Bi2Se3(0 0 0 1) surface

“…[16], the interaction is limited to the very interfacial region (few atomic layer), without significant interdiffusion at RT. The absence of variations in the morphology at RT as observed by SEM (contrary, for example, to Ag on Bi2Se3 [34]) in the timescale of weeks confirm this. The fact that the spectral weight of Bi2 with respect to Bi1 rapidly increase while Se2 does not with respect to Se1, is ascribed to diffusion of Bi atoms into Au towards the surface of the metal islands, while Se remains localized at the interface region, which is mostly not detected with XPS, except for the very peripheral region.…”

Control of Spin–Orbit Torques by Interface Engineering in Topological Insulator Heterostructures

“…[5][6][7][8][9][10] However, the experiments have been mainly performed with highly doped TIs (Bi 2 Se 3 , Bi 2 Te 3 , and Sb 2 Te 3 ) in which the topological states coexist with bulk bands at the Fermi level and contribute only marginally to the electrical conduction, especially at room temperature. 11 Furthermore, the analysis of the results follows the implicit assumption that the TI/FM interface is perfectly abrupt, despite existing reports demonstrating the presence of magnetic dead layers, 8,12 strong intermetallic alloying, [12][13][14] and band bending. [15][16][17] Alternative torque mechanisms were disregarded under such an assumption.…”

A cryogenic solid-state reaction at the interface between Ti and the Bi2Se3 topological insulator

“…21 In a previous study we showed that TIs have the power to oxidize even noble metal atoms already at RT (Ag, see ref. 22), which is quite unusual and suggests the presence of a catalytic effect within the studied system. Our hypothesis is that the TSS electrons participate in the reaction by catalyzing it.…”

“…This indicates that, after the formation of the interfacial phases, the reaction stops, contrary to what happens for Ag. 22 However, the observed chemical interaction has dramatic macroscopic consequences when the Ti coverage increases to a certain threshold. At higher coverage (40 nm), the surface develops a network of hollow buckles of different mesh sizes as shown in Fig.…”

“…A redox solid-state reaction at room temperature (RT) was observed at the Ag/Bi 2 Se 3 interface, which yielded AgSe 2 , AgBiSe 2 and metallic Bi. 22 In addition, chemical reactions at the metal/TI interface have been detected for Fe, 20,[23][24][25][26] Cr, 20,27 Co, Ni, 20 Mn and Cu. 28 Interdiffusion of Cu into Bi 2 Te 3 was observed by Kong et al 29 who studied how the orientation of Bi 2 Te 3 influences the resistivity of Cu metal contact.…”