METHOD OF CHEMICAL DEPOSITION OF IRIDIUM OXIDE FILM ON RIGID SUBSTRATE

Abstract

A method of chemical deposition of Iridium oxide film on rigid substrate is provided. The method comprises providing a rigid substrate in a container, adding an iridium precursor and mixing the iridium precursor with water to form an iridium precursor liquid in the container, adding and mixing an oxidant with the iridium precursor liquid in the container; and depositing an iridium oxide film on the rigid substrate in the container. A chelating agent and pH adjustor can be either selectively used for stabilizing the chemical bath deposition and for adjusting pH value of the liquid. For a variety of rigid substrates to be applied, the pH adjustor can adjust the pH value within a range of 413. By employing the proposed fabrication method, it is extraordinarily advantageous of chemical alkaline as well as chemical acid deposition formula with configuration of depositing sodium-doped IrO.sub.x iridium oxide film.

Claims

1. A method of chemical deposition of iridium oxide film on rigid substrate, comprising: providing a rigid substrate in a container; adding an iridium precursor and mixing said iridium precursor with water to form an iridium precursor liquid in said container; adding and mixing an oxidant with said iridium precursor liquid in said container; and depositing an iridium oxide film on said rigid substrate in said container.

2. The method of chemical deposition of iridium oxide film on rigid substrate according to claim 1, wherein said iridium precursor is selected from a group consisting of Na.sub.3IrCl.sub.6, K.sub.3IrCl.sub.6, IrCl.sub.3, IrBr.sub.3, Na.sub.2IrCl.sub.6, K.sub.2IrCl.sub.6, and (NH.sub.4).sub.2IrCl.sub.6.

3. The method of chemical deposition of iridium oxide film on rigid substrate according to claim 1, wherein said oxidant is selected from a group consisting of NaClO, NaClO.sub.2, KClO, NaBrO.sub.3, Ca(ClO).sub.2, and a mixture of NaClO, NaClO.sub.2, KClO, NaBrO.sub.3, Ca(ClO).sub.2 and H.sub.2O.sub.2.

4. The method of chemical deposition of iridium oxide film on rigid substrate according to claim 1, wherein said rigid substrate is made of Ti, TiW, Al, Ni, Au, Pt, Ptlr, stainless steel or indium tin oxide (ITO).

5. The method of chemical deposition of iridium oxide film on rigid substrate according to claim 1, wherein a reaction temperature of said method when taking place in an environment of 1 atmosphere (atm) is in a range of 0-100 C.

6. The method of chemical deposition of iridium oxide film on rigid substrate according to claim 1, wherein a concentration of said iridium precursor liquid is in a range of 0.01 mM-1 M.

7. The method of chemical deposition of iridium oxide film on rigid substrate according to claim 1, wherein a concentration of said oxidant is in a range of 8 M2 M.

8. The method of chemical deposition of iridium oxide film on rigid substrate according to claim 1, after step of forming said iridium precursor liquid in said container, further comprising: adding a chelating agent in said iridium precursor liquid for preventing unexpected Iridium particles forming in said liquid.

9. The method of chemical deposition of iridium oxide film on rigid substrate according to claim 1, before step of depositing said iridium oxide film on said rigid substrate in said container, further comprising: adding a pH adjustor for adjusting a pH value of said liquid.

10. The method of chemical deposition of iridium oxide film on rigid substrate according to claim 8, wherein said chelating agent is Malonate, succinate, tartrate, citrate, oxalate, EDTA-2Na or a mixture of Malonate, succinate, tartrate, citrate, oxalate, and EDTA-2Na.

11. The method of chemical deposition of iridium oxide film on rigid substrate according to claim 9, wherein said pH adjustor is NaOH, KOH, TABOH, or HNO.sub.3.

12. The method of chemical deposition of iridium oxide film on rigid substrate according to claim 9, wherein said pH adjustor adjusts said pH value of said liquid within a range of 413.

13. The method of chemical deposition of iridium oxide film on rigid substrate according to claim 1, wherein a deposition rate of said iridium oxide film is in a range of 0.31.76 nm/min.

14. The method of chemical deposition of iridium oxide film on rigid substrate according to claim 1, wherein said iridium oxide film is alternatively Na-doped, and a mole ratio of sodium (Na) to iridium (Ir) is in a range of 04.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings:

[0016] FIG. 1 shows a flow chart of a method of chemical deposition of iridium oxide film on rigid substrate in accordance with one embodiment of the present invention.

[0017] FIGS. 2A, 2B, 2C, and 2D show sequential fabrication illustrations according to a first embodiment of the present invention employing the method of chemical deposition of iridium oxide film on rigid substrate.

[0018] FIG. 2E shows an illustrative diagram of the product of iridium oxide film deposited on a rigid substrate according to a first embodiment of the present invention.

[0019] FIGS. 3A, 3B, and 3C show sequential fabrication illustrations according to a second embodiment of the present invention employing the method of chemical deposition of iridium oxide film on rigid substrate.

[0020] FIG. 3D shows an illustrative diagram of the product of iridium oxide film deposited on a rigid substrate according to a second embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

[0022] The embodiments described below are illustrated to demonstrate the technical contents and characteristics of the present invention and to enable the persons skilled in the art to understand, make, and use the present invention. However, it shall be noticed that, it is not intended to limit the scope of the present invention. Therefore, any equivalent modification or variation according to the spirit of the present invention is to be also included within the scope of the present invention.

[0023] In order to overcome the conventional problems, the proposed solution of the present invention provides a method of chemical deposition of iridium oxide film on a rigid substrate, which adopts a chemical alkaline as well as chemical acid deposition formula for depositing sodium-doped IrO.sub.x iridium oxide film. With a variety of precursors being chosen, for example, K.sub.3IrCl.sub.6, IrCl.sub.3, IrBr.sub.3, or K.sub.2IrCl.sub.6, the iridium oxide film can be sodium-doped free as well. By employing the chemical deposition method of the present invention, the iridium oxide film can be selectively deposited on various rigid substrates to obtain an IrO.sub.x film with high uniformity. Moreover, owing to the excellent biocompatibility of the IrO.sub.x film, it is advantageous of being applied as stimulating electrodes for implantable future biomedical devices.

[0024] Please refer to FIG. 1, which shows a flow chart of a method of chemical deposition of iridium oxide film on rigid substrate in accordance with one embodiment of the present invention. The proposed method of the present invention comprising the following steps:

[0025] Step S100: providing a rigid substrate in a container.

[0026] Step S102: adding an iridium precursor and mixing the iridium precursor with water to form an iridium precursor liquid in the container.

[0027] Step S104: adding and mixing an oxidant with the iridium precursor liquid in the container; and

[0028] Step S106: depositing an iridium oxide (IrO.sub.x) film on the rigid substrate in the container.

[0029] Since what the present invention expected is to deposit uniform iridium oxide (IrO.sub.x) film on the rigid substrate, a chelating agent can be further added in the iridium precursor liquid for preventing unexpected iridium particles forming in the liquid according to a preferred embodiment of the present invention.

[0030] Moreover, according to the present invention, the rigid substrate where the expected iridium oxide (IrO.sub.x) film is grown upon can be selectively made of Ti, TiW, Al, Ni, Au, Pt, Ptlr, stainless steel or indium tin oxide (ITO). In addition, various types of substrates have different resistance to acidity and alkalinity. In order to make the liquid condition and/or environment suitable for the acidity and/or alkalinity tolerance of the substrate, a pH adjustor for adjusting a pH value of the liquid in the container might be necessary and can be further employed in the present invention depending on practical needs.

[0031] Please find Table 1, which shows a shortlist of a plurality of available formula for implementing the proposed method of chemical deposition of iridium oxide film on rigid substrate of the present invention.

TABLE-US-00001 TABLE 1 chelating precursor agent pH adjustor oxidant Final pH Na.sub.3IrCl.sub.6 Malonate NaOH NaClO 12~13 K.sub.3IrCl.sub.6 succinate KOH NaClO.sub.2 12~13 IrCl.sub.3 tartrate TABOH KClO 12~13 IrBr.sub.3 citrate HNO.sub.3 NaBrO.sub.3 12~13 Na.sub.2IrCl.sub.6 oxalate NaClO + H.sub.2O.sub.2 4~9 K.sub.2IrCl.sub.6 EDTA-2Na Ca(ClO).sub.2 12~13 (NH.sub.4).sub.2IrCl.sub.6 w/o chelating agent

[0032] As shown, the iridium precursor can be selected from a group consisting of Na.sub.3IrCl.sub.6, K.sub.3IrCl.sub.6, IrCl.sub.3, IrBr.sub.3, Na.sub.2IrCl.sub.6, K.sub.2IrCl.sub.6, and (NH.sub.4).sub.2IrCl.sub.6. Alternatively, the iridium precursor the present invention uses can be also selected as a mixture of all the above mentioned iridium precursor including Na.sub.3IrCl.sub.6, K.sub.3IrCl.sub.6, IrCl.sub.3, IrBr.sub.3, Na.sub.2IrCl.sub.6, K.sub.2IrCl.sub.6, and (NH.sub.4).sub.2IrCl.sub.6.

[0033] According to a preferred embodiment of the present invention, the chelating agent can be chosen as Malonate, succinate, tartrate, citrate, oxalate, or EDTA-2Na. Alternatively, according to other embodiment of the present invention, the chelating agent being employed by the proposed invention can be also selected as a mixture of all the above mentioned chelating agents including Malonate, succinate, tartrate, citrate, oxalate, and EDTA-2Na. People skilled in the art are allowed to make or create equivalent modification or variation according to the spirits of the present invention, whereby is still to be also included within the scope of the proposed invention.

[0034] The pH adjustor can be either NaOH, KOH, TABOH, or HNO.sub.3.

[0035] Nevertheless, it should be noticed that the formula of the present invention can be prepared with or without these chelating agent and/or pH adjustor, depending on pH concentration of the liquid, acidity and/or alkalinity tolerance of the substrate, deposition stability of the IrO.sub.x film and so on. In other words, the chelating agent and/or the pH adjustor listed as above are mainly optional, and can be selectively disposed according to a variety of needs, specifications, liquid conditions, and so on.

[0036] Regarding the choice of oxidant being used in the present invention, the oxidant can be selected from a group consisting of NaClO, NaClO.sub.2, KClO, NaBrO.sub.3, Ca(ClO).sub.2, and a mixture of NaClO, NaClO.sub.2, KClO, NaBrO.sub.3, Ca(ClO).sub.2 and H.sub.2O.sub.2. It is important to observe that a final pH value of the liquid in the formula is more likely in a range of 1213, showing alkalinity. However, when the oxidant is a mixture of NaClO and H.sub.2O.sub.2, the final pH of the liquid solution can be decreased to be in a range of 413, possibly showing acidity. Under such circumstances, substrates having poor tolerance with alkalinity while better tolerance with acidity can be employed and prepared according to such embodiment of the present invention, by which the proposed method of chemical deposition of iridium oxide film on rigid substrate of the present invention can be extensively applied, especially for iridium oxide (IrO.sub.x) film to be grown on the rigid substrate which is mostly acid resistant

[0037] Furthermore, please refer to FIGS. 2A, 2B, 2C, and 2D which show sequential fabrication illustrations according to a first embodiment of the present invention employing the method of chemical deposition of iridium oxide film on rigid substrate. FIG. 2E shows an illustrative diagram of the product of iridium oxide film deposited on a rigid substrate according to such a first embodiment of the present invention.

[0038] In the first embodiment shown in FIG. 2A, at first, a rigid substrate 20 is provided and fixed with tape 11 as vertically in a glass container 22. It is important to emphasize hereinafter that according to the present invention, the rigid substrate 20 we use could be placed in any steps, and the order is not aimed to limit the scope of the present invention. What we disclosed merely helps to illustrate one exemplary embodiment of the present invention. As such, the proposed invention is not limited thereto.

[0039] An iridium precursor liquid 30, such as potassium hexachloroiridate (III), K.sub.3IrCl.sub.6, is prepared (as described in step S102 in FIG. 1) and added into the container 22 as shown FIG. 2B. Later on, a chelating agent (0.01-0.5 M tartrate) 40 and a pH adjustor (0.1-1 M sodium hydroxide, NaOH) 50 are sequentially added and mixed up with the iridium precursor liquid 30 in FIG. 2C. In one embodiment, the chelating agent 40 can be added before the pH adjustor 50. Alternatively, the pH adjustor 50 can be added before the chelating agent 40. It draws our attention that the orders of these ingredients to be put and mixed up are not intended to limit the scope of the present invention but merely to show an exemplary embodiment of the present invention. For people skilled in the art having understandings and technical solutions to the present invention, various modifications and changes are allowed to be followed without departing from the scope of the invention and yet still fall into the invention scope of the present application.

[0040] Later in FIG. 2D, an oxidant 60, such as sodium hypochlorite, NaClO, is added so that the chemical bath and electro-less deposition occurs. In FIG. 2E, when the chemical bath deposition (CBD) reaction which usually takes 15 minutes, or even up to 72 hours is complete, the CBD-IrO.sub.2 film 70 is successfully deposited on the rigid substrate 20, having its uniform film thickness approximately 40-80 nm.

[0041] According to the embodiment of the present invention, since the proposed chemical bath deposition (CBD) reaction is most likely taking place in an environment of 1 atmosphere (atm), such reaction temperature of the proposed fabrication method will be in a range of 0-100 C. However, while the chemical bath deposition (CBD) reaction is taking place under a variety of atmospheric pressure range, then the reaction temperature varies accordingly as well.

[0042] A concentration of the iridium precursor liquid is in a range of 0.01 mM-1 M, and a concentration of the oxidant is in a range of 8 M2 M. By properly controlling the deposition rate of our iridium oxide film in a range of 0.3-1.76 nm/min, the IrO.sub.x film thickness is adjustable and estimable depending on the chemical bath deposition reaction time.

[0043] In another aspect, please find FIGS. 3A, 3B, and 3C, which show sequential fabrication illustrations according to a second embodiment of the present invention employing the method of chemical deposition of iridium oxide film on rigid substrate. FIG. 3D shows an illustrative diagram of the product of iridium oxide film deposited on a rigid substrate according to such a second embodiment of the present invention.

[0044] At first, a rigid substrate 20 is provided and fixed with tape 11 as vertically in a glass container 22 as shown in FIG. 3A. What differs from the first embodiment as mentioned earlier is that, the iridium precursor liquid 30 and the chelating agent 40 can be mixed in the container 22 as shown in FIG. 3B, and the pH adjustor 50 and the oxidant 60 can be mixed in another container 22 as shown in FIG. 3C. Next, the container 22 as shown in FIG. 3B comprising the rigid substrate 20, the iridium precursor liquid 30 and the chelating agent 40 and the container 22 as shown in FIG. 3C comprising the pH adjustor 50 and the oxidant 60 are mixed together. As such, in FIG. 3D when the chemical bath deposition reaction is complete, the CBD-IrO.sub.2 film 70 is successfully deposited on the rigid substrate 20.

[0045] In view of all, from these two various embodiments, it is apparent that the formula in which these orders of ingredients are put together does not intend to limit the scope of the present invention. The proposed method of chemical deposition of iridium oxide film on rigid substrate employed by the present invention mainly comprises at least following steps of providing an iridium precursor liquid in the container, and mixing an oxidant with the iridium precursor liquid in the container so as to achieve the purpose of depositing an iridium oxide (IrO.sub.x) film on the rigid substrate as claimed. Therefore, it is believed that for those who are skilled in the art, various modifications and variations can be made to the present invention without departing from the scope or spirit of the invention while still fall into the scope of the invention and its equivalent.

[0046] Moreover, according to the present invention, the method of chemical deposition of iridium oxide film on rigid substrate mainly adopts a chemical bath deposition (also known as electro-less deposition). Since the whole formulation is involved with solution processes, and the content of the formula can optionally comprise sodium ions (Na.sup.+). Based on the contents, for example iridium precursors, oxidants, and/or pH adjustor, chelating agent being selected, the IrO.sub.x film product of the present invention may possibly contain sodium, and the concentration of the sodium content can be properly designed according to different formula solution adjustments. Overall, a mole ratio of sodium (Na) to iridium (Ir) can be set in a range of 0-4, so the iridium oxide film is alternatively Na-doped.

[0047] As a result, to sum up, a novel method of chemical deposition of iridium oxide film on rigid substrate has been provided in the present invention for configuration as well as implementations. By using such a chemical bath deposition method, the iridium oxide is able to deposit on a variety of desirable rigid substrates having different acidity and alkalinity tolerance. Since the iridium oxide (IrO.sub.x) film is well characterized by its chemical stability, biocompatibility, and high charge storage capacity (up to 16.8 mC/cm.sup.2), it has been always a better choice as the material for various biomedical devices, such as bio-stimulation electrodes and carriers of the cells. Moreover, by further relevant annealing taken along with a plurality of processes subsequently, the thickness of the iridium oxide (IrO.sub.x) film can be increased, which will be beneficial to improve the cell growth for both the human-machine interface and orientated substrates.

[0048] It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the invention and its equivalent.