The present invention relates to a combinatorial electrochemical deposition system enabling computer control over parameters and allowing for systematic exploration of the parameter space.
Electrodeposition can be used for making many different materials ranging from bulk materials, films, nanowires, and nanoparticles. The material can be metals, semiconductors, insulators, superconductors or have multiple components. Very importantly the materials can be amorphous, nanocrystalline, or single crystalline which can have very dramatic affect on the properties of the deposit. The deposits and the properties depend upon how the conditions of deposition are controlled.
Literature often cites the conditions used to make a sample with a few of the key parameters, which usually include applied potential, concentration of the ion to be reduced, identity of the supporting electrolyte and temperature. If the system is robust enough, the results can be reproduced from this information.
Often times another lab will have difficulty in reproducing this because not all the parameters are identified. Seldom disclosed information such as exact geometry of the electrochemical cell, the type of isolation from the reference electrode, contamination of the starting reagents water, cleaning method of the equipment, pH, dissolved oxygen content and many other parameters may have a huge impact on the morphology and ultimately on the reproducibility of the system. In addition most publications do not tell the full story because experiments were done one at a time, in a serial manner within a small variation of the parameter space.
Principal aspects of the present invention are to provide a combinatorial electrochemical deposition system enabling computer control over parameters and allowing for systematic exploration of the parameter space.
Other important aspects of the present invention are to provide such combinatorial electrochemical deposition system substantially without negative effect and that overcome some of the disadvantages of prior art arrangements.
In brief, a combinatorial electrochemical deposition system is provided for enabling computer control over multiple parameters and allowing for systematic exploration of the parameter space. The combinatorial electrochemical deposition system includes a computer providing system control and data acquisition functions. The computer controls a plurality of pumps, each pump is connected to a respective material supply sources. The plurality of pumps is coupled via a mixer and a plurality of distribution valves of a cell and fluidics distribution network to deposit a particular composition of materials or solution concentration to individual electrochemical cells of an electrochemical cell array. The computer controls the mixer and the plurality of distribution valves. The electrochemical cell array includes a plurality of singly addressable flow-through isolatable electrochemical cells with a common working electrode. Each of the electrochemical cells includes a counter electrode and a reference electrode.
In accordance with features of the invention, the combinatorial electrochemical deposition system includes a multi-channel potentiostat coupled to the computer for applying a selected voltage potential to the common working electrode, and to the counter electrode and the reference electrode of each of the electrochemical cells. Demultiplexing electronics are coupled to the computer and the multi-channel potentiostat for applying the selected voltage potential to the counter electrode and the reference electrode of each of the electrochemical cells. The material supply sources include a supporting electrolyte, a selected metal of interest, and predetermined additives. The predetermined additives include, for example, pH modifiers, complexing agents, and surface-active adsorbents.
In accordance with features of the invention, the reference electrode includes a capillary saturated calomel electrode (SCE) reference electrode. The counter electrode includes a platinum counter electrode. The working electrode includes a unitary sheet member supporting a container of each of the electrochemical cells. The working electrode can be implemented by a single crystal silicon wafer or a substantially uniform thin film deposited across a single wafer.
In accordance with features of the invention, the container of each of the electrochemical cells includes a cylindrical container, such as a glass tube, or a glass plate with a plurality of holes. A glass rod is coupled to a set of the electrochemical cells and is selectively moved between a fill position and a bypass position for opening and closing the set of electrochemical cells.
The present invention together with the above and other objects and advantages may best be understood from the following detailed description of the preferred embodiments of the invention illustrated in the drawings, wherein:
Having reference now to the drawings, in
In accordance with features of the invention, a Combinatoral Electrochemical Deposition System 100 is provided for implementing total computer control over generally all parameters and that allows for systematic exploration of the parameter space. Computer automation is provided for all tasks from mixing of the solutions to rates of filling and controlling the potential and treatment of the sample post deposition.
In accordance with features of the invention, Combinatoral Electrochemical Deposition System 100 enables rapid high throughput for materials synthesis and rapid testing. Combinatoral Electrochemical Deposition System 100 enables systematic exploration of complex multi-dimensional parameter space and automation of multiple tedious tasks. Combinatoral Electrochemical Deposition System 100 typically is an aqueous system that can be implemented with generally inexpensive instrumentation, while Combinatoral Electrochemical Deposition System 100 does not necessarily have to be aqueous. Combinatoral Electrochemical Deposition System 100 implements a programmed self-assembly process.
Computer 102 is coupled to a plurality of pumps 104. Each of the multiple pumps 104 is connected to a respective supply source 106 containing, for example, a supporting electrolyte, a selected metal of interest, a predetermined additive, and a pH modifier. Computer 102 controls an electrochemical deposition of materials of a selected composition.
Combinatoral Electrochemical Deposition System 100 includes an exemplary cell and fluidics distribution network generally designated by the reference character 200 including an array 202 of electrochemical cells 204. A common working electrode (WE) 206 of the preferred embodiment is provided for the multiple cells 204 of the electrochemical cell array 202. The common working electrode (WE) 206 of the preferred embodiment advantageously can be implemented with a single crystal silicon wafer or a substantially uniform thin film deposited across a single wafer.
Cell and fluidics distribution network 200 implements a much different approach to the problem than has been used in conventional arrangements. Most conventional arrangements for combinatorial electrochemistry have utilized a common bath, with a common reference electrode for an array of working electrodes. While this conventional method of manufacture can be much simpler, there are many problems with diffusion from one electrode's environment to another and having separate working electrodes that may differ in composition, unlike a single crystal silicon wafer or a uniform thin film deposited across a single wafer. There are also many problems with systems that are open to the atmosphere allowing contamination. Likewise, systems that perform experiments without being able to control all the parameters like solution mixing and fluidics distribution may suffer from irreproducibility.
Cell and fluidics distribution network 200 is the heart of the Combinatoral Electrochemical Deposition system 100. As shown in
Combinatoral Electrochemical Deposition System 100 includes demultiplexing electronics 108 and a multi-channel potentiostat 110, both coupled to and controlled by computer 102. Computer 102 controls the potentiostat 110 which controls the potential applied to a particular cell 204 and period of time the selected potential is applied to each cell 204 within the electrochemical cell array 206 and records the data generated which is relayed back to the computer 102 for storage and further analysis. Multi-channel potentiostat 110 is operatively controlled by computer 102 to provide a“virtual ground” to the working electrode 206 by connection to the ports labeled W via a connection 112.
Multi-channel potentiostat 110 and demultiplexing electronics 108 are operatively controlled by computer 102 to provide a plurality of selected reference electrode potentials indicated by ports labeled R via the demultiplexing electronics 108 to the electrochemical cell array 206. Multi-channel potentiostat 110 and demultiplexing electronics 108 are operatively controlled by computer 102 to provide one or a plurality of controlled counter electrode potentials indicated by multiple ports labeled C via the demultiplexing electronics 108 to the electrochemical cell array 206.
Combinatoral Electrochemical Deposition System 100 includes a mixer 114 and a plurality of distribution valves 116 coupled between the pumps 104 and the electrochemical cell array 202, and coupled to computer 102. Computer 102 controls the mixing of solutions and rates of filling of the electrochemical cell array 202. An output waste flow from the electrochemical cell array 202 is collected in a waste vessel 120. After an electrochemical deposition process is completed, a gas, such as argon, is blown through the electrochemical cell array 202 to empty all the multiple cells 204
Various computers can be used to implement computer 102, such as personal computer using the commercial program Labview® functioning as a data acquisition computer system by executing two way communication with the system 100 via serial port, parallel port, GPIB, TCP/IP or a data acquisition (DAQ) interface. A commercially available multi-channel potentiostat manufactured and sold by Princeton Applied Research, Ametek® can be used for the multi-channel potentiostat 110. Masterflex® computer controlled peristaltic pumps can be used for the plurality of pumps 104.
Referring also to
A capillary SCE (saturated calomel electrode) reference electrode can be used to implement reference electrode 210, while other reference electrode types such as MSE (mercurous sulfate electrode), Ag/AgCI electrode, quasi-reference electrode also can be used. The counter electrode 212 includes a generally circular disk 220 having a pair of generally centrally disposed, spaced apart openings 222, 224 respectively for receiving the cell input 214 and cell outlet 216. A third opening 226 in the circular disk 220 of the counter electrode 212 is provided for receiving the reference electrode 210. The wire attached 212 to the circular disk 220 provides electrical contact to the counter electrode.
For example, a platinum counter electrode can implement the counter electrode 212, while the counter electrode 212 may also be implemented by a platinized titanium, gold or any other metal inert to modification or dissolution under the conditions being studied.
In accordance with features of the invention, the independent electrochemical cells 204 of Combinatoral Electrochemical Deposition System 100 avoid cross contamination and mass transport from adjacent electrodes. The electrochemical cells 204 being constructed of inert materials enables consistent results to be obtained after aggressive cleaning with reagents known to clean contaminants to the highest degree possible such as concentrated sulfuric acid and concentrated nitric acid. Avoidance of materials such as base metals, polyethylene, silicone, nylon and other non-fluorinated plastics prevents trace contamination of the solutions or electrode surfaces, which can be problematic for obtaining pure, consistent electrochemistry. Combinatoral Electrochemical Deposition System 100 combines both synthesis and characterization in the single system. The separate electrochemical cells 204 of Combinatoral Electrochemical Deposition System 100 allow systematic exploration of solution concentration, which is a very important parameter affecting conditions of growth and are necessary to change for characterization. Combinatoral Electrochemical Deposition System 100 enables ease of connection and allows experimentation with generally any parameter within, for example, more than a 20 dimensional parameter space. Combinatoral Electrochemical Deposition System 100 includes sealed and integrated robotic mixing and fluidic distribution network 200 enabling cleanliness without requiring a clean room environment.
Each electrochemical cell 204 is singly addressable flow-through isolatable electrochemical cell. For example, different selected potentials are applied via the demultiplexing electronics 108 to the respective counter electrode 212 of the singly addressable electrochemical cells 204 with respect to the respective reference electrode 210 for each cell. The potentiostat connection 112 to the working electrode (WE) 206 hold the WE at virtual ground, while the potential is sensed by the individual reference electrodes 210 of respective electrochemical cells 204 which provides a feedback mechanism and allows the potentiostat 110 to raise or lower the potential of the counter electrode 212 until the desired potential is achieved at the working electrode 206. Because a single common working electrode 206 is used for the electrochemical cell array 202 allows a homogenous single silicon wafer to be used to define the working electrode 206 for all the singly addressable electrochemical cells 204. This is an important feature of Combinatoral Electrochemical Deposition System 100.
The electrochemical cell 204 including a generally cylindrical, stepped container 230 mounted on the common WE 206 within a masked off area 232 of a wafer defining the common WE 206. It should be understood that the container 230 is not necessarily stepped. For example, the container 230 can be defined by a single diameter container, such as shown in
As shown in
Referring to
As shown, electrochemical cell array portion 300 includes multiple electrochemical cells 204 with one shown mounted within a support structure 302. Support structure 302 includes a base member 304 supporting an upper member 306. The base member 304 is a glass member that is bonded with the upper member 306, for example, formed of Teflon. Support structure 302 includes a plurality of stepped openings 308, each for receiving a respective electrochemical cell 204. An opening extends through the upper Teflon member 306 for receiving the fluid pathway 238 that is received through the multiple electrochemical cells 204.
Referring to
Referring to
As shown in
Electrochemical cell array 600 is defined by a plurality of identical blocks 604 secured together by a pair of tie rods 606. Each block 604 contains five electrochemical cells 602, as shown in
Referring also to
The glass rods 610 include notches 612 respectively positioned relative to the channels 608 to admit inflow to the cell 602 from flow path channel 608 and outflow from the cell 602 to the channel 608. Then the notches 612 of glass rods 610 are selectively moved to position bypass grooves 614 into a bypass position for the cells 602, operatively controlled by computer 102 via an air cylinder or solenoid (not shown in
Referring to
Electrochemical cell array 800 includes a plurality (nine) of glass rods 804 extending horizontally and a plurality (nine) of flow path channels 806 extending diagonally, at 60° from the glass rods 804, as shown in
While the present invention has been described with reference to the details of the embodiments of the invention shown in the drawing, these details are not intended to limit the scope of the invention as claimed in the appended claims.
This application claims the benefit of U.S. Provisional Application No. 60/704,558, filed on Aug. 2, 2005.
The United States Government has rights in this invention pursuant to Contract No. W-31-109-ENG-38 between the United States Government and Argonne National Laboratory.
Number | Date | Country | |
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60704558 | Aug 2005 | US |