Microscopic and Electronic Structure of Semimetallic Sb and Semiconducting AlSb Fabricated by Nanoscale Electrodeposition:  An in Situ Scanning Probe Investigation

Abstract

The nanoscale electrocrystallization of pure Sb and the compound semiconductor AlSb on Au(111) has been studied by in situ scanning probe techniques (STM and STS) employing an ionic liquid electrolyte, {AlCl3-[C4mim]+Cl-} (1:1) containing SbCl3. The characteristic changes of the electronic structures with varying potentials have been probed for the first time by normalized differential conductance spectra, (dI/dU)/(I/U). In the underpotential deposition range of Sb the formation of two layers is observed. For the first monolayer a (square root 3 x square root 3)R30 degrees structure is determined from atomically resolved STM images. During the deposition and dissolution of the Sb monolayers characteristic wormlike or spinodal structures appear indicating surface alloying of antimony with the gold substrate. Under overpotential conditions two different Sb structures have been observed. If the deposition potential is continuously stepped to -0.1 V, Sb nanostripes form. On the other hand, randomly dispersed small clusters occur if the potential is jumped from 0.0 to -0.3 V vs Al/Al(III). Both modifications exhibit typical semimetallic behavior as shown by the STS spectra. At -1.1 V the cyclic voltammogram shows a clear reduction wave that is assigned to AlSb compound formation. Deposits in this potential range are characterized by a homogeneous distribution of clusters with diameters of approximately 20 nm. Conductance spectra of these clusters exhibit the main features of the electronic structure of the bulk semiconductor AlSb, with a band gap of 2.0 +/- 0.2 eV. Electrodeposition experiments on both sides of the compound deposition potential show a strong doping effect that is manifest in the corresponding conductance spectra.

The Electrode/Ionic Liquid Interface: Electric Double Layer and Metal Electrodeposition

“…[32,113] The systems include elemental semiconductors of Ge [115][116][117][118][119] and Si [120] and composite semiconductors of Si x Ge 1Àx , [121] ZnTe, [122] CdTe, [123] , InSb, [124] AlSb, [125,126] and ZnSb. [127] More recently, efforts have been devoted to the preparation of functionalized and nanostructured semiconductors, [128][129][130][131] including nanowires of Ge [128] , Si, [128] and Si x Ge 1Àx [130] as well as three-dimensional ordered macroporous Ge.…”

“…Systematic in situ STM investigations of the UPD of these two systems have been carried out on Au singlecrystalline electrodes, which demonstrate a significant "solvent effect" from ionic liquids. [22,67,69,125,126,151,152] The results from the authors' group in [BMI] [BF 4 ] [22,67,69,153] are highlighted as follows.…”

“…In the basic [BMI]Cl-AlCl 3 on Au(111), nanostrips and randomly dispersed nanoclusters have been observed for Sb, [126,151] while in the acidic [BMI]Cl-AlCl 3 on Au(111), needle-like structures or ultrathin films occur for Bi, [152] both depending on whether their UPD layers are formed. In addition, a temperature effect on the Sb OPD on a GC electrode in [EMI] [BF 4 ] has been investigated, [162] and it was found that a high temperature favors the formation of a crystalline structure.…”

Electrodeposition of Semiconductors in Ionic Liquids

“…The electrodeposition of AlSb in ionic liquids was investigated by several groups. It was reported that AlSb can be electrodeposited on Au (111) [34,35]. In situ probe techniques were used to study the electrodeposition of the semiconductor.…”

Electric field assisted processing and characterization of AlSb nanocrystals

“…One of them is AlSb, which has wide variety applications e photovoltaic cells, pen junction diodes, and anodes for Li-ion batteries [1]. It is zinc-blende structure with a lattice constant of 0.6126 nm [2,3], and high melting point (1058 C) [4]. It shows sharp-line donor-acceptor pair spectrum, caused by electron-hole transition process [2].…”