T. Djenizian

Selective palladium electrochemical deposition onto AFM-scratched silicon surfaces

The present work investigates the selective electrochemical deposition of palladium nano-structures into scratches produced through thin oxide layers covering p -Si (1 0 0) surfaces. Using an atomic force microscope equipped with a single-crystalline diamond tip scratches in the 100 nm range were produced through a 10 nm thick dry oxide layer. Pd deposition was carried out in PdCl2 (0.01 g l � 1 )� /HCl (0.1 M) by cathodic potential steps. Investigation of the palladium nucleation and growth processes onto silicon surfaces is presented. Under optimized conditions sub-100 nm palladium structures can be obtained with a very high selectivity. # 2003 Elsevier Ltd. All rights reserved.

Atomic Force Microscopy-Induced Nanopatterning of Si(100) Surfaces

In this study, we investigate the possibilities of selectively electrodepositing Cu on surface defects created in p-type and n-type Si(100) by scratching the surface with the tip of an atomic force microscope (AFM). Nanosized grooves were produced on Si surfaces with a diamond-coated AFM tip at heavy forces. Cu was electrodeposited on these grooved surfaces from a 0.01 M CuSO 4 + 0.05 M H 2 SO 4 electrolyte under various conditions. The results clearly show that defects created on H-terminated p-type Si(100) lead to an enhanced reactivity, i.e., preferential Cu deposition at such defects is possible. However, a much higher degree of selectivity of the deposition is obtained if AFM-induced grooves are produced on surfaces that carry a native oxide layer. The masking effect of this insulator film is demonstrated by selective Cu electrodeposition into scratches on oxide-covered p- and n-type silicon. After an optimization of electrochemical parameters, we achieved the deposition of uniform and well-defined nanostructures. The process presented here opens new perspectives for selective electrodeposition and direct patterning of Si surfaces.

Morphological characterization of porous InP superlattices

Abstract Porous superlattices n-type (100) InP are produced electrochemically on by changing the applied current or potential periodically in 1 M HCl + 1 M HNO3 solutions. The superlattice consists of stack of alternating two layers with various morphologies and porosities. The plan-view morphologies of the top surface of superlattice were almost same, and the pore size was varied in the nano-order range. On the other hand, the cross-sectional morphologies depend strongly on the electrochemical condition. For low applied currents or potentials such as 10 mA or 1.5 VAg/AgCl, respectively, porous layers with a facet-like structure were formed. The size of each facet did not change with the etching time, but the number of the facets increased with time. For high currents or potentials such as 50, 100 mA or 3 VAg/AgCl, respectively, a tree-like structure with random and/or tangled branches was observed. At a still higher potential of 5 VAg/AgCl, the porous layer exhibited fairly regular array of straight pores. Therefore, it is found that the morphology of the porous layer can be highly controlled by the applied current or potential.

Factors in Electrochemical Nanostructure Fabrication Using Electron-Beam Induced Carbon Masking

Department of Materials Science, LKO, University of Erlangen-Nuremberg, D-91058 Erlangen, GermanyThe present work investigates the fabrication of Au nanostructures using the masking effect of carbon patterns deposited by theelectron-beam~E-beam! of a scanning electron microscope for electrochemical reactions. E-beam induced deposition is based onthe decomposition of residual hydrocarbon species ~molecules from the pump oil! to create a solid deposit at the point of impactof the E-beam. Subsequently, such E-beam deposited matter is used to completely block the electrochemical deposition of Au inthe nanometer scale. In this work, several factors affecting the resolution of the process are studied. Electrochemical conditions aswell as control of the E-beam C-deposit are investigated to optimize the lateral resolution of the process. Especially, it isdemonstrated that the beam energy used for depositing the C-mask plays a crucial role in fabricating Au nanostructures in thesub-50 nm range.© 2004 The Electrochemical Society. @DOI: 10.1149/1.1643744# All rights reserved.Manuscript received April 2, 2003. Available electronically February 5, 2004.

Electron-beam induced carbon deposition used as a mask for cadmium sulfide deposition on Si(100)

The present work investigates the use of carbon masks, deposited on n-type Si(100) surfaces in a scanning electron microscope (SEM), for electrochemical nanopatterning. Carbon contamination lines were written at different electron doses on the n-type Si(100) surfaces and characterized by AFM. Subsequently, deposition of CdS was carried out by electrodeposition of Cd from a 1 mM CdF2+0.05 M NaF solution followed by a chemical treatment in 1 M Na2S. CdS deposits were prepared under various electrochemical conditions and were characterized by SEM, scanning Auger electron spectroscopy and optical techniques including fluorescence and photoluminescence measurements. It is demonstrated that under optimized electrochemical conditions carbon deposits of less than 1 nm thickness and in a width of 100 nm range can act as a negative resist, i.e. can block the deposition of CdS completely and selectively and thus can be used for nanopatterning.

ALD Al2O3-Coated TiO2 Nanotube Layers as Anodes for Lithium-Ion Batteries

The utilization of the anodic TiO2 nanotube layers, with uniform Al2O3 coatings of different thicknesses (prepared by atomic layer deposition, ALD), as the new electrode material for lithium-ion batteries (LIBs), is reported herein. Electrodes with very thin Al2O3 coatings (∼1 nm) show a superior electrochemical performance for use in LIBs compared to that of the uncoated TiO2 nanotube layers. A more than 2 times higher areal capacity is received on these coated TiO2 nanotube layers (∼75 vs 200 μAh/cm2) as well as higher rate capability and coulombic efficiency of the charging and discharging reactions. Reasons for this can be attributed to an increased mechanical stability of the TiO2 nanotube layers upon Al2O3 coating, as well as to an enhanced diffusion of the Li+ ions within the coated nanotube layers. In contrast, thicker ALD Al2O3 coatings result in a blocking of the electrode surface and therefore an areal capacity decrease.

Electron Beam Induced Writing of Corrosion Protection

Carbon patterns (C layers) were deposited on iron surfaces by electron-beam induced contamination decomposition writing. Chemical and electrochemical etching were used to investigate the protective nature of these C layers against metal corrosion. The results clearly show that E-beam written C patterns can be very corrosion resistant. The key factor controlling the degree of protectiveness, under given conditions of attack, is the deposition dose, i.e., the layer thickness. For sufficiently high doses, the iron surface can be completely protected against corrosion. Therefore, this direct masking approach opens new perspectives for highly precise and controlled local corrosion suppression.

Selective Titanium Oxide Formation Using Electron-beam Induced Carbon Deposition Technique

The present work describes the selective titanium oxide formation based on electron-beam (e-beam) induced carbon deposition used as a mask against chemical dissolution. Under ideal conditions the C-deposits act as a negative resist to hinder the titanium oxide dissolution at e-beam treated locations. Carbon patterns were written in a scanning electron microscope at different electron doses on titanium oxide electrochemically grown in 1 M NaOH by potentiostatic experiments. Subsequently, the untreated areas were chemically removed in 0.5 % HF leaving the C-protected TiO 2 patterns at the Ti surface. The selectivity of the technique depends on several factors such as the electron dose during masking and the chemical parameters. Under ideal conditions, it is demonstrated that direct patterning of surfaces as well as the fabrication of microstructures can be achieved using such technique.

A Semiconductor Nano-Patterning Approach Using AFM-Scratching through Oxide Thin Layers

Abstract : AFM-scratching was performed through thin oxide layer which was either a native oxide layer (1.5 - 2 nm thick) or a thermal oxide layer (10 nm thick). Due to their insulating properties, the SiO2 films act as masks for the metal electrochemical deposition. In the scratched openings copper deposition can take place selectively and thus nano-scale metal lines could be successfully plated onto the p-type silicon substrates. Using particularly, if sufficiently thick thermal oxide has advantages over the native oxide, it allows a H-termination of the Si within the grooves (HF treatment) without eliminating the oxide layer on the rest of the surface.