Formation of Ru Nanotubes by Atomic Layer Deposition onto an Anodized Aluminum Oxide Template

Lee, Do-Joong; Yim, Sung-Soo; Kim, Ki-Su; Kim, Soohyun; Kim, Ki-Bum

doi:10.1149/1.2901542

Cited by 40 publications

(18 citation statements)

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“…In addition to the metals described above, the ALD of other metals, including Ru [204][205][206][207][208][209][210][211][212][213], Rh [63,[214][215][216], Co [175,217,218], Fe [175], Mo [219], and W [220][221][222][223], have been reported. However, the application of these metals to catalysis has thus far been limited.…”

Section: Other Metals Aldmentioning

confidence: 99%

“…Rh(acac) 3 is the commonly used precursor for Rh ALD[63,[214][215][216]. A wide variety of ALD Ru precursors have been explored including metallocenes, β-diketonates, and their derivatives[204][205][206][207][208][209][210][211][212]. Among these, the most widely studied and applied Ru ALD precursors are metallocenes and their .…”

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confidence: 99%

“…Reprinted with permission from[66]. Copyright © 2015, American Chemical Society.As pointed out previously, this oxygen-based, combustion-type noble metal ALD typically requires temperatures above 200 °C (~300°C in most cases), to burn off the organic ligands[65,106,[204][205][206][207][208][209][210][211]224]. In order to reduce the growth temperature for broader applications, Hämäläinen and coworkers demonstrated that Ir, Rh, Pt and Pd ALD can be performed at a significantly lower temperature by using ozone and molecular hydrogen as co-reactants in an ABC-type ALD process (also seen in the review paper[65] and the references therein)[63,64].…”

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confidence: 99%

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Atomic layer deposition—Sequential self-limiting surface reactions for advanced catalyst “bottom-up” synthesis

Elam

Stair

2016

Surface Science Reports

270

215

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Catalyst synthesis with precise control over the structure of catalytic active sites at the atomic level is of essential importance for the scientific understanding of reaction mechanisms and for rational design of advanced catalysts with high performance. Such precise control is achievable using atomic layer deposition (ALD). ALD is similar to chemical vapor deposition (CVD), except that the deposition is split into a sequence of two self-limiting surface reactions between gaseous precursor molecules and a substrate. The unique self-limiting feature of ALD allows conformal deposition of catalytic materials on a high surface area catalyst support at the atomic level. The deposited catalytic materials can be precisely constructed on the support by varying the number and type of ALD cycles. As an alternative to the wet-chemistry based conventional methods, ALD provides a cycle-by-cycle "bottom-up" approach for nanostructuring supported catalysts with near atomic precision. In this review, we summarize recent attempts to synthesize supported catalysts with ALD. Nucleation and growth of metals by ALD on oxides and carbon materials for precise synthesis of supported monometallic catalyst are reviewed. The capability of achieving precise control over the particle size of monometallic nanoparticles by ALD is emphasized. The resulting metal catalysts with high dispersions and uniformity often show comparable or remarkably higher activity than those prepared by conventional methods. For supported bimetallic catalyst synthesis, we summarize the strategies for controlling the deposition of the secondary metal selectively on the primary metal nanoparticle but not on the support to exclude monometallic formation. As a review of the surface chemistry and growth behavior of metal ALD on metal surfaces, we demonstrate the ways to precisely tune size, composition and structure of bimetallic metal nanoparticles. The cycle-by-cycle "bottom up" construction of bimetallic (or multiple components) nanoparticles with near atomic precision on supports by ALD is illustrated. Applying metal oxide ALD over metal nanoparticles can be used to precisely synthesize nanostructured metal catalysts. In this part, the surface chemistry of Al 2 O 3 ALD on metals is specifically reviewed. Next, we discuss the methods of tailoring the catalytic performance of metal catalysts including activity, selectivity and stability, through selective blocking of the low-coordination sites of metal nanoparticles, the confinement effect, and the formation of new metal-oxide interfaces. Synthesis of supported metal oxide catalysts with high dispersions and "bottom up" nanostructured photocatalytic architectures are also included. Therein, the surface chemistry and morphology of oxide ALD on oxides and carbon materials as well as their catalytic performance are summarized.

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Section: Other Metals Aldmentioning

confidence: 99%

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Atomic layer deposition—Sequential self-limiting surface reactions for advanced catalyst “bottom-up” synthesis

Elam

Stair

2016

Surface Science Reports

270

215

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“…24,26 This oxygen-based, combustion-type noble metal ALD typically requires relatively high temperature above 200°C (near 300°C in most cases), to burn off the organic ligands. [13][14][15][16][17][18][19][20]25,27,28 The most well-studied Ru ALD precursor is bis(ethylcyclopentadienyl)ruthenium (Ru(EtCp) 2 ). 15,17,18,29 Kang et al demonstrated Ru ALD at near 300°C using Ru(EtCp) 2 with oxygen; 15 Park and co-workers further showed the growth temperature can be lowered to 225°C using Ru(EtCp) 2 with ozone.…”

Section: ■ Introductionmentioning

confidence: 99%

Low Temperature ABC-Type Ru Atomic Layer Deposition through Consecutive Dissociative Chemisorption, Combustion, and Reduction Steps

Elam

2015

Chem. Mater.

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Thermal atomic layer deposition (ALD) of noble metals is frequently performed using molecular oxygen as the nonmetal precursor to effect combustion-type chemistry at r e l a t i v e l y h i g h t e m p e r a t u r e s o f 3 0 0°C . B i s -(ethylcyclopentadienyl)ruthenium (Ru(EtCp) 2 ) is one of the commonly used metal precursors for Ru ALD. Using Ru(EtCp) 2 and oxygen as reactants, Ru ALD was achieved at near 300°C. Here, we demonstrate that Ru ALD can proceed at as low as 150°C by using successive exposures to oxygen and hydrogen as the coreactants. In situ quartz crystal microbalance (QCM) and quadrupole mass spectroscopy (QMS) measurements both suggest that this ABC-type ALD occurs through dissociative chemisorption, combustion, and reduction for the Ru(EtCp) 2 , oxygen, and hydrogen steps, respectively, in a similar manner to processes using ozone and hydrogen as coreactants reported previously. Moreover, we believe this molecular O 2 and H 2 based ABC-type ALD could be exploited for the ALD of other noble metals to decrease the deposition temperature and reduce oxygen impurities. ■ INTRODUCTIONUltrathin conformal Ru films have been used as electrodes in a variety of microelectronics applications including positivechannel metal oxide semiconductor (PMOS) metal gates and dynamic random access memory (DRAM) capacitors, due to the high work function (4.7 eV), low bulk resistivity (7.1 μΩ· cm), good thermal stability, and, more importantly, oxygen diffusion barrier property of Ru. 1−5 As the size of semiconductor devices decreases according to Moore's Law, complicated three-dimensional (3-D) nanostructures will be needed to achieve high storage capacities. 6−9 As a consequence, the requirements for conformality, thickness control, and low temperature of the Ru deposition process become more severe. Among the various thin film deposition techniques, atomic layer deposition (ALD) is considered to be the most promising for meeting these requirements. 10−12 Ruthenium ALD has been widely explored using a variety of Ru precursors including metallocenes, β-diketonates, and their derivatives. 13−21 In these studies, molecular oxygen is most often employed as the nonmetal precursor for thermal Ru ALD. As with similar noble metal ALD processes utilizing O 2 (e.g., Pt, Rh, and Ir), the Ru ALD is thought to follow a combustiontype mechanism in which the metal organic precursor first reacts with surface oxygen to burn off a fraction of the ligands, and then the rest of the ligands are further combusted in the subsequent oxygen exposure step. The oxygen exposure also serves to replenish the surface oxygen through dissociation on the noble metal surface. Carbon dioxide and water are the major gaseous products formed during the two half reactions, 13,22−25 while in some cases dehydrogenation can also occur. 24,26 This oxygen-based, combustion-type noble metal ALD typically requires relatively high temperature above 200°C (near 300°C in most cases), to burn off the organic ligands. [13][14][15][16][17][18][19][20]25,27,28 Th...

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“…Both USPI's and KPI's laboratories have accumulated experiences on preparing the AAO templates, as reflected in many of their articles [7][8][9][10][11][12][13] and these experiences greatly eased this pursuit. As target materials, we used thermally evaporated Bi film and CNT film formed by a membrane infiltration method.…”

Section: D) Thermoelectric Power Enhancement Via An Aao-templated Nanmentioning

confidence: 99%

Nano-Material and Structural Engineering for Thermal Highways

Kim¹,

Xu²,

Lyeo³

2013

Self Cite

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The AOARD-KRF 'thermal management' project has led to several developments and breakthroughs driven by collaborative efforts between the Korean groups (Seoul National University and KRISS) and the group at Brown University. Two main objectives were set for the project: improvement of thermoelectric efficiency and demonstration of "thermal diodes" with heat-flow rectification. Both objectives were successfully met, and in fact, exceeded.One breakthrough -thermal-voltage imaging with unprecedented atomic resolution that exceeds classical limits is particularly noteworthy. It was unanticipated at the start but propelled by growing interests arising from this effort. It will likely extend its impact beyond thermal management into basic sciences for years to come.Several strategies for improving thermal functionality in electronic materials were implemented via AIPEL patterning, AAO-templated nanomesh formation and atomic-layered doping. Thermal rectification effects have been ascertained by engineering into the structure phase-changing and strongly temperature dependent materials. An ultrathin (~40nm) film that is infrared (heat) reflecting, light-transmitting (>90%), highly conductive (~1000 S/cm) and also EMI-shielding (>20dB) stands out as another example outcome of the exploration of an atomic-layer engineering approach. It could lead to defense and civilian applications in near term.A novel concept of self-regulated cooling, inspired by nature (e.g. human skin sweating), was implemented, tested, and proven to be effective. This success, however still preliminary, opens a pathway to explorations of wearable, scalable, distributed, self-powered cooling and temperature regulation, as well as to its underlying science of phase-transitions in nano-capillary fluidics.

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Formation of Ru Nanotubes by Atomic Layer Deposition onto an Anodized Aluminum Oxide Template

Cited by 40 publications

References 18 publications

Atomic layer deposition—Sequential self-limiting surface reactions for advanced catalyst “bottom-up” synthesis

Atomic layer deposition—Sequential self-limiting surface reactions for advanced catalyst “bottom-up” synthesis

Low Temperature ABC-Type Ru Atomic Layer Deposition through Consecutive Dissociative Chemisorption, Combustion, and Reduction Steps

Nano-Material and Structural Engineering for Thermal Highways

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