Structure and shape transformation from multiply twinned particles to epitaxial nanocrystals: Importance of interface on the structure of Ag nanoparticles

Li, B. Q.; Zuo, Jian‐Min

doi:10.1103/physrevb.72.085434

Cited by 28 publications

(27 citation statements)

References 37 publications

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“…The ring diffraction pattern of Ag comes from the growth of Ag MTPs of random orientation on the H-Si͑001͒, which was observed by TEM. 14 Lower surface energy of the H-terminated Si is responsible for the particle growth of Ag. 15 The TEM study shows that annealing of as-deposited Ag nanoparticles lead to a structural change from MTPs to fcc epitaxial nanocrystals.…”

Section: Methodsmentioning

confidence: 99%

“…14 The driving force for the transition comes from the strain energy of the Ag MTPs and a possible change in interfacial energy at the Ag-Si interface. 14 The driving force appears large enough that even MTPs with diameters as small as 2 nm transform into fcc nanocrystals. Thus Ag nanoparticles on H-Si͑001͒ are ideal for studying the size dependence of transformation from MTP to fcc.…”

Section: Introductionmentioning

confidence: 99%

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Size-dependent structural transition from multiple-twinned particles to epitaxial fcc nanocrystals and nanocrystal decay

et al. 2007

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The size dependence of structural transition from multiple-twinned particles ͑MTP͒ to epitaxial face centered cubic nanocrystals was investigated for Ag nanoparticles formed on Si͑001͒ surfaces by in situ reflection high-energy electron diffraction and ex situ transmission electron microscopy. The transition from MTP to nanocrystals was promoted by postdeposition annealing. Clear particle size dependence is found in the epitaxial formation temperatures ͑T E ͒, which is about 2 / 3 of the calculated, size-dependent, melting temperature ͑T M ͒ using the value of surface energy ␥ S =1.2 J/m 2 for larger particles ͑Ͼ2 nm͒. Once nanocrystals are formed, they decay and disappear in a narrow temperature range between 795 and 850 K. No evidence of nanocrystal melting was detected from the reflection high-energy electron diffraction observations.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Size-dependent structural transition from multiple-twinned particles to epitaxial fcc nanocrystals and nanocrystal decay

et al. 2007

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“…Compared to Au that prefers nanocrystal formation, 8 Ag can form a number of intermediate structures, including multiply twinned NCs. [9][10][11] While the growth characteristics of Ag on TiO 2 ͑110͒ surfaces have been studied by several groups, [12][13][14] there is no systematic study of the structure evolution and epitaxy formation of Ag NCs on TiO 2 ͑110͒, as far as we know. Temperature dependent studies are important, in general, for understanding the effect of sintering on the structure of NCs.…”

Section: Introductionmentioning

confidence: 99%

“…18,19 TEM offers the ability to image the individual NCs and obtain local structural data. 10,11 The combination of these two techniques offers a unique perspective of metal NCs growth on oxide surfaces. We study the structural evolution of Ag NCs on TiO 2 ͑110͒ as a function of temperature up to sublimation.…”

Section: Introductionmentioning

confidence: 99%

Structural evolution, epitaxy, and sublimation of silver nanoclusters on TiO2 (110)

Sivaramakrishnan

Tedjasaputra

Sato

et al. 2010

Journal of Applied Physics

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The structural evolution, epitaxy, and sublimation temperature of silver nanoclusters ͑NCs͒ on TiO 2 ͑110͒ surfaces prepared in two different ways are reported here based on a combination of in situ reflection high energy electron diffraction characterization and ex situ electron imaging. It is shown that silver NCs deposited at room temperature on oxidized TiO 2 ͑110͒ surfaces are unable to form a single epitaxy prior to sublimation. When heated close to sublimation, two particle orientations dominate: ͑111͒Ag ʈ ͑110͒TiO 2 , ͓−110͔Ag ʈ ͓001͔TiO 2 and ͑112͒Ag ʈ ͑110͒TiO 2 , ͓−110͔Ag ʈ ͓001͔TiO 2 . Single twinned silver NCs are found to be stable even at temperatures close to sublimation. On the other hand, silver NCs prepared similarly on reduced TiO 2 ͑110͒ surfaces behave very differently when heated to higher temperatures. On the reduced surface, the NCs are able to evolve into a single epitaxy-͑111͒Ag ʈ ͑110͒TiO 2 , ͓−110͔Ag ʈ ͓001͔TiO 2 . The sublimation temperature for silver NCs on the reduced surface is found to be less than those on the oxidized surface by about 35°. The epitaxy formed by annealing is the same as the one formed by depositing silver onto reduced TiO 2 ͑110͒ at 350°C ͑Ͼ0.5 T m of Ag͒.

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“…To observe the shape transition from islands to wires, Ag nanoclusters (islands) were first formed by depositing Ag on hydrogen terminated Si(001) [ 2,3 ]. The experiment was performed on an IBM-built LEEM maintained at the Materials Research Laboratory, University of Illinois UrbanaChampaign (UIUC).…”

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In-situ Observation of Ag Nanowire Growth on Si(001)

Li¹,

Świȩch²,

Zuo³

2007

MAM

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Understanding how nanowires (NWs) grow is an important materials physics issue that not only improves our knowledge of crystal growth but also can have a large impact on our ability to self-assemble controlled nanostructures. Currently, NWs are synthesized by catalytic growth, selfassembly on supporting substrates or in solution without catalyst. Catalytic growth is believed to proceed through the vapor-liquid-solid (VLS) mechanism where the liquid-solid interface controls the growth direction. Nanowries grown without catalysts include transition, or rare-earth, metal silicide wires and fcc metals like Ag. In the latter case, it is generally assumed that NWs grow due to the competition between the strain and surface energies that favors one-dimensional structure above a certain size limit [ 1 ]. In case of Ag nanowires on Si(001), Tersoff and Tromp [ 1 ] reported that wires are grown rotated by 45˚ with Ag[100]||Si[110] and a 6% misfit strain between Ag and Si. This strain is then used to explain the Ag nanowire growth. However, the orientation relationship reported by Tersoff and Tromp is very different from previous report on Ag films grown on Si(001). To examine whether the nanowires adapt a different epitaxial relationship than thin films and to study the nanowire growth, we carried out a combined low-energy electron microscopy (LEEM) and transmission electron microscopy (TEM) investigation.To observe the shape transition from islands to wires, Ag nanoclusters (islands) were first formed by depositing Ag on hydrogen terminated Si(001) [ 2, 3 ]. The experiment was performed on an IBM-built LEEM maintained at the Materials Research Laboratory, University of Illinois UrbanaChampaign (UIUC). In-situ observation of NW growth was achieved by following the evolution of nanometer-sized Ag islands during annealing using LEEM. After growth in a adjacent growth chamber the substrate was transferred to the LEEM and annealed under 10 -9 Pa. Micrometer long Ag NWs were formed by depositing Ag at 210 °C and subsequent annealing at temperatures between 400 °C and 450 °C. Ex-situ TEM observations were performed on samples pre-thinned for electron transparency and chemically prepared H-terminated Si(001). Figure 1 shows the growth of two clusters; one grows into a NW while the other into a rectangular island (in projection). The wire growth occurred during annealing at 450˚C of 5 ML Ag deposited at 300˚C on H-Si(001)for a period of 270 seconds. The growth process was captured by LEEM in the early stage of the growth starting from a nanoparticle. Initially, the two Ag clusters were too small to be observed (nominal LEEM resolution is 10 nm). After 6 seconds of observation, two clusters became visible (Fig. 1 top-left). Afterward, one of the two clusters at the lower position start to grow toward the other cluster to form a wire. To quantify the growth process, we measured the width and length of the NW. Using the initial positions of the clusters as reference, we further divided the length into L1 and L2, corresponding to the g...

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Structure and shape transformation from multiply twinned particles to epitaxial nanocrystals: Importance of interface on the structure of Ag nanoparticles

Cited by 28 publications

References 37 publications

Size-dependent structural transition from multiple-twinned particles to epitaxial fcc nanocrystals and nanocrystal decay

Size-dependent structural transition from multiple-twinned particles to epitaxial fcc nanocrystals and nanocrystal decay

Structural evolution, epitaxy, and sublimation of silver nanoclusters on TiO2 (110)

In-situ Observation of Ag Nanowire Growth on Si(001)

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