Growth of IrO₂ Films and Nanorods by Means of CVD: An Example of Compositional and Morphological Control of Nanostructures

Abstract

was evaluated over a circular area measuring roughly 500 lm in diameter [13]. After deposition, each of the samples was inspected using an optical stereomicroscope and a scanning electron microscope (SEM) equipped with an energy-dispersive spectrometer. Growth of IrO 2 Films and Nanorods by Means of CVD: An Example of Compositional and Morphological Control of Nanostructures**By Reui-San Chen, Yi-Sin Chen, Ying-Sheng Huang,* Yao-Lun Chen, Yun Chi, Chao-Shiuan Liu, Kwong-Kau Tiong, and Arthur J. Carty Iridium dioxide, IrO 2 , belongs to the family of transition metal oxides that exhibit metallic conductivity at room temperature. It has been used in applications such as optical switching layers in electrochromic devices, [1] and durable electrode materials for chlorine or oxygen evolution.[2]Moreover, owing to its excellent resistance to the inter-diffusion of oxygen, as well as high thermal and chemical stability, [3] IrO 2 films serve as electrodes for high-density dynamic random access memory (DRAM), or nonvolatile ferroelectric random access memory (NVFRAM), devices.[4] Related investigations have indicated that polarization fatigue of PZT ferroelectric capacitors can be effectively suppressed by using IrO 2 thin film electrodes. [5] In recent reports, IrO 2 was also used to fabricate field-emission cathodes for microelectronic devices and field-emission displays.[6]As a result of these diverse applications, there is a growing need to develop easy and reliable methods for growing IrO 2 phases, either as thin films, or in other physical forms. Various methods such as reactive magnetron sputtering, [7] pulsed laser deposition, [8] and annealing of Ir films in an O 2 atmosphere, [9] have been employed for this purpose. However, CVD, a technique that possesses several advantages including better composition control, high deposition rate, excellent step coverage, and suitability for scale-up, [10] has not yet been successfully employed for IrO 2 even though Ir thin films are normally obtained using O 2 as the carrier gas to prevent carbon iridium metal impurities from being incorporated into the deposited film. [11] Recently, the influence of O 2 partial pressure on the formation of IrO 2 using (MeCp)Ir(COD)/O 2 as the reactive gas mixture, has been discussed by Maury and Senocq. [12] In this communication, we wish to report the successful deposition of IrO 2 thin films using the cold-wall CVD method. Moreover, by optimizing experimental parameters, the formation of distinct, rod-like, aligned IrO 2 nanocrystals can be observed, with good control of growth perpendicular to the substrate surfaces. The structural composition, surface morphology, and spectroscopic properties of the resulting IrO 2 materials are discussed.The reactive mixture (CpMe)Ir(COD)/O 2 was used in CVD experiments that were conducted under three different pressure settings, 1 torr, 10 torr, and 30 torr, while deposition temperatures were separated into six settings ranging from 250 C to 500 C. The combined X-ray diffraction (XRD) pattern...

Iridium Metal Thin Films and Patterned IrO2 Nanowires Deposited Using Iridium(I) Carbonyl Precursors

“…This preliminary result indicates that such low-pressure reaction conditions are highly effective for inducing clean conversion to iridium metal. [17] XRD analysis confirmed the polycrystalline nature of the deposited material by showing a statistical distribution of both (111) and (200) diffraction signals expected for the bulk iridium metal (Fig. 5).…”

Raman scattering characterization of well‐aligned RuO2 and IrO2 nanocrystals

“…This additional shift has been attributed to the residual stress effect induced by tensile strain. 19 Rosenblum et al 15 reported the observation of a blueshift of the three strongest lines induced by hydrostatic pressure in 24 The first investigation of the Raman scattering of IrO 2 NCs was by Chen et al 20 The samples were grown via the MOCVD technique at temperatures in range of 300-450°C, which exhibited randomly oriented, vertically aligned nanorods (NRs). The average length and radius of these IrO 2 NRs were estimated to be 3.5 š 0.2 µm and 150 š 50 nm, respectively ( Fig.…”

Growth and characterization of iridium dioxide nanorods

“…Recently, such a nanosized IrO 2 tip has been realized using metalorganic chemical vapor deposition (MOCVD) technique [14]. In this report, a detailed characterization for the IrO 2 nanorods grown on Si(1 0 0) substrate are carried out.…”