Monitoring Nanoscale Surface Changes During Electrochemical Deposition Using NTEGRA Instruments from NT-MDT

Topics Covered

Background
Introduction
Monitoring Nanoscale Changes using NTEGRA
Hardware Information
Electrochemical Cell
Electronics
SPM
Probes

Background

NT-MDT Co. was established in 1991 with the purpose to apply all accumulated experience and knowledge in the field of nanotechnology to supply researchers with the instruments suitable to solve any possible task laying in nanometer scale dimensions. The company NT-MDT was founded in Zelenograd - the center of Russian Microelectronics. The products development are based on the combination of the MEMS technology, power of modern software, use of high-end microelectronic components and precision mechanical parts. As a commercial enterprise NT-MDT Co. exists from 1993.

Introduction

Electrochemical (EC) technologies attract constantly rising interest because it is the way for controlled modifications of the surface even with atomic precision. EC deposition is a widely used approach for creation of thin metal films with unique properties. On the other hand EC dissolution allows imitation and study of corrosion processes.

Monitoring Nanoscale Changes using NTEGRA

Scanning probe microscopy i.e. Atomic Force Microscopy (AFM) and Scanning Tunneling Microscopy (STM) techniques open up the possibility to monitor the nanometer scaled changes occurring at the surface during an EC modification. With the NTEGRA nanolaboratory one can run various EC experiments in highly specialized conditions.

As an example the imagesin Figure 1 shows that the external magnetic field (MF) strongly influences the Cu deposition process. Due to magneto-hydrodynamic (MHD) Electro-deposition Electro-deposition + convection and some other effects of interaction of ions with external MF the electrodeposition occurs much faster.

Figure 1. AFM images of copper films electro-deposited on Au (111) without magnetic field (a1) and in magnetic field (B = 0.1 T) (a2). Scans were obtained by using CSG01 probes. The in situ AFM investigations were performed with the NTEGRA Aura setup in the MFM configuration. Scans size 2x2 µm.

Figure 2 demonstrate the possibilities of STM. During Cu electro-deposition it is allowed to see the formation and destruction of a lattice with the copper adatoms and the sulfate anions. As a result, the Cu monolayer replaces the sulfate anions. The in situ STM investigations were performed with the NTEGRA setup designed for electrochemical measurements.

Figure 2. STM images of the under potential deposition (UPD) of copper on Au (111) in sulfate solution before negative shifting the sample potential (b1) and afterwards (b2). After Fourier filtration (b3, b4), it is obvious that negative shifting leads to the replacement of sulfate anions by Cu adatoms: atomic structure typical for sulfate ( √3 x √3)R30° changes to structure (1 x 1) typical for pseudo morphic Cu monolayer. Scans size 30 x 30 nm.

Hardware Information

Electrochemical Cell

EC cell for STM and AFM experiments in controlled environment provides thermostabilization. Hermetic cell is optionally available.

Electronics

Bipotentiostat is a computer-controlled module for electrochemical experiments in potentiostatic, potentiodynamic and galvanostatic modes.

SPM

NTEGRA AURA is a Scanning Probe Microscope for studies in the conditions of controlled environment and low vacuum. The Q-factor of the cantilever in vacuum increases, thus gaining the sensitivity, reliability and accuracy of "probe-sample" light forces measurements. At that, the change from atmosphere pressure to 10^-2 Torr vacuum provides the tenfold gain of Q-factor.

By further vacuum pumping, Q-factor reaches its plateau and changes insignificantly. Thus, NTEGRA AURA presents the optimal "price/quality" ratio: comparing to the high-vacuum devices it needs much less time - only one minute - to get the vacuum that is needed for the tenfold Q-factor increase. At the same time the system is compact and easy to operate and maintain. As the NTEGRA platform product, NTEGRA AURA has built-in closed loop control for all the axes, optical system with 1 µm resolution and ability to work with more than 40 different AFM methods.

NTEGRA AURA setup in the MFM configuration allows to perform EC experiments in external magnetic field.

Probes

Conventional High Resolution AFM "Golden" Silicon Probes (CSG01) for contact mode are available with different coatings (Au, Al, PtIr, TiN, Au, diamond doped conductive e.t.c.) and tipless. Probes without any coating and for non-contact modes can be supplied as well.

Source: NT-MDT Co.

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