Investigations on the Electrochemical Atomic Layer Growth of Bi2Se3 and the Surface Limited Deposition of Bismuth at the Silver Electrode

Abstract

The Electrochemical Atomic Layer Deposition (E-ALD) technique is used for the deposition of ultrathin films of bismuth (Bi) compounds. Exploiting the E-ALD, it was possible to obtain highly controlled nanostructured depositions as needed, for the application of these materials for novel electronics (topological insulators), thermoelectrics and opto-electronics applications. Electrochemical studies have been conducted to determine the Underpotential Deposition (UPD) of Bi on selenium (Se) to obtain the Bi2Se3 compound on the Ag (111) electrode. Verifying the composition with X-ray Photoelectron Spectroscopy (XPS) showed that, after the first monolayer, the deposition of Se stopped. Thicker deposits were synthesized exploiting a time-controlled deposition of massive Se. We then investigated the optimal conditions to deposit a single monolayer of metallic Bi directly on the Ag.

Underpotential‐Assisted Electrodeposition of Highly Crystalline and Smooth Thin Film of Bismuth

“…The electrochemical behaviour of bismuth on Ag(111) is shown in Figure 1: a strong UPD peak is present at À 0.36 V, while the bulk deposition starts above À 0.47 V. The deposition of bismuth has been performed both in presence and in absence of an underlying UPD layer, which was obtained by applying a potential of À 0.45 V for 3 minutes. [44] The atomic surface density of Ag(111) (cell constant 4.08 Å) is 1.39 • 10 19 atm/m 2 , then the deposition of one monolayer (ML) on the electrode surface involves 665 μC/cm 2 . In our case, the deposited charge, estimated from the anodic peak, is 345 μC/cm 2 , [44] corresponding to a coverage of 0.52 ML when referred to a monolayer of Ag(111).…”

“…We found also that bismuth exhibits UPD on silver, probably due to its semi-metal behaviour or to the formation of an alloy, and we have also optimised the experimental conditions for the UPD of bismuth on Ag(111). [44] In this work, we grew a uniform and crystalline deposit of bismuth without using any other precursor than the element itself. Since the UPD potential only allows the deposition of bismuth in direct contact with the silver substrate, the layers above the first one was deposited through an overpotential deposition (bulk deposition).…”

“…The process typically occurs between metals and non-metals and has been previously used by our research group to synthesize various binary and ternary semiconductors and alloys [39][40][41][42][43] including Bi 2 Se 3 . [44] Starting from the bismuth compound, we took a step further with the selective electrodesorption-based atomic layer deposition (SEBALD): [45,46] in fact, selenium stripping led to an uniform and crystalline thin film of bismuth, [47] that it would otherwise have been difficult to obtain with the direct bulk deposition over the Nernst potential. We found also that bismuth exhibits UPD on silver, probably due to its semi-metal behaviour or to the formation of an alloy, and we have also optimised the experimental conditions for the UPD of bismuth on Ag(111).…”

Electrochemical Atomic Layer Epitaxy Deposition of Ultrathin SnTe Films

“…The ECALE method has been employed to deposit a variety of semiconductors, such as CdTe, Bi 2 Se 3 , CdSe, CdS, Ge x Sb y Te z , etc. [6,[11][12][13][14][15][16]. According to our knowledge, deposition of SnTe thin films using the ECALE method has not been reported so far.…”

Optimization and Characterization of Electrodeposited Cadmium Selenide on Monocrystalline Silicon

“…The semiconductor nature of Si makes finding the right deposition conditions a difficult task since the exchange of electrons between the electrode and the solution is severely limited compared to metal electrodes and is influenced by the lighting conditions. While the deposition of CdSe on metals is now a well-known practice in the scientific field [36][37][38][39], as well as other semiconductors (CdS [40], MoSe 2 [41], Bi 2 Se 3 [42]), its deposition on Si has been scarcely explored.…”