Quantum Size Effects in the Growth, Coarsening, and Properties of Ultra-thin Metal Films and Related Nanostructures

Özer, Mustafa M.; Wang, Cai‐Zhuang; Zhang, Zhenyu; Weitering, Hanno H.

doi:10.1007/s10909-009-9905-z

Cited by 39 publications

(64 citation statements)

References 65 publications

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“…Specifically, a 25% distance corresponds to an oscillation period of 8 monolayers (ML) [8,12]. This oscillating behaviour can be attributed to quantum size effects [21].…”

Section: Structural Properties Of Ultrathin Mg and Alloyed Filmsmentioning

confidence: 98%

First-principles studies of hydrogen interaction with ultrathin Mg and Mg-based alloy films

2011

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The search for technologically and economically viable storage solutions for hydrogen fuel would greatly benefit from research strategies that involve systematic property tuning of potential storage materials via atomic-level modification. Here, we use first-principles density functional theory (DFT) to theoretically investigate the structural and electronic properties of ultrathin Mg films and Mg-based alloy films and their interaction with atomic hydrogen.Additional delocalized charges are distributed over the Mg films upon alloying them with 11.1% of Al or Na atoms. These extra charges contribute to enhance the hydrogen binding strength to the films. We calculated the chemical potential of hydrogen in Mg films for different dopant species and film thickness, and included the vibrational degrees of freedom. By comparing the chemical potential with that of free hydrogen gas at finite temperature (T) and pressure (P), we construct a hydrogenation phase diagram and identify the conditions for hydrogen absorption/desorption. The formation enthalpies of metal hydrides are greatly increased in thin films, and in stark contrast to its bulk phase, the hydride state can only be stabilized at high P and T (where chemical potential of free H 2 is very high). Metal-doping increases the thermodynamic stabilities of the hydride films and thus significantly helps to reduce the required pressure condition for hydrogen absorption from H 2 gas. In particular, with Na alloying hydrogen can be absorbed/desorbed at experimentally accessible T and P conditions.

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“…Specifically, a 25% distance corresponds to an oscillation period of 8 monolayers (ML) [8,12]. This oscillating behaviour can be attributed to quantum size effects [21].…”

Section: Structural Properties Of Ultrathin Mg and Alloyed Filmsmentioning

confidence: 98%

First-principles studies of hydrogen interaction with ultrathin Mg and Mg-based alloy films

2011

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“…16 Subsequent stable layer thicknesses follow a bilayer pattern up to 12 ML, indicative of strong quantum size effects on the growth. 6,16 Following the procedure in Ref. 16, we determined that the film thickness inside the holes is 2 ML so that the total film thickness in regions between these "blind" holes equals 8 ML.…”

Section: Resultsmentioning

confidence: 99%

“…Interesting examples include the formation of optically active quantum dots and quantum-dot superlattices in Si/Ge 1 and PbSe/PbTe heteroepitaxy, 2 metallic nanowires in silicide heteroepitaxy, 3,4 or the formation of atomically smooth metal films on semiconductor surfaces. 5,6 While the formation of wires and dots appears to be driven by a classical strain relaxation mechanism, the formation of atomically-smooth metal films is often driven by quantum-mechanical confinement. 6,7 The substrate is essential in both cases because it determines the strain energy and quantum mechanical boundary conditions of the films.…”

Section: Introductionmentioning

confidence: 99%

“…5,6 While the formation of wires and dots appears to be driven by a classical strain relaxation mechanism, the formation of atomically-smooth metal films is often driven by quantum-mechanical confinement. 6,7 The substrate is essential in both cases because it determines the strain energy and quantum mechanical boundary conditions of the films. [6][7][8][9][10] Atomically-clean substrate surfaces are often reconstructed.…”

Section: Introductionmentioning

confidence: 99%

“…6,7 The substrate is essential in both cases because it determines the strain energy and quantum mechanical boundary conditions of the films. [6][7][8][9][10] Atomically-clean substrate surfaces are often reconstructed. The surface reconstruction can be altered or eliminated by deposition of (sub)-monolayer (ML) amounts of a third species, prior to thin film deposition.…”

Section: Introductionmentioning

confidence: 99%

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Influence of interface reconstruction on the formation and superconductive properties of metastable Pb-Ga alloy films

et al. 2011

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We show that the growth, composition, and superconductive properties of ultrathin Pb1−xGax alloy films depend strongly on the atomic structure of the substrate interface. Whereas alloy films on the Si(111)-(7 × 7) surface grow in multilayers, reminiscent of the quantum growth phenomenon observed in pure Pb layers, alloy films on the Si (111)• -Ga interfaces gradually switch to classical layer-by-layer growth. The (7 × 7) interface is unique in that it enables formation of atomically smooth alloy films containing up to 6% of Ga, which is far beyond the solid solubility limit. In contrast, the ( √ 3 × √ 3) interfaces promote phase separation. The contrasting influences of these interfaces are also reflected by their superconductive properties, most notably by the differences in the critical current density, exceeding more than one order of magnitude.

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Quantum Size Effects in the Growth and Properties of Ultrathin Metal Films, Alloys, and Related Low-Dimensional Structures

Jia

Özer

Weitering

et al. 2010

Nanophenomena at Surfaces

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This chapter addresses the quantum mechanical nature of the formation, stability, and properties of ultrathin metal films, metallic alloys, and related lowdimensional structures, with Pb as a primary elemental example. The emphasis is on the contribution to the overall energetics from the electronic degrees of freedom of the low-dimensional systems. As a metal film reduces its thickness, the competition between quantum confinement, charge spilling, and Friedel oscillations, all of electronic origin, can dictate whether an atomically smooth film is marginally, critically, or magically stable or unstable against roughening during the growth of such metal films. The "electronic growth" mode as emphasized here serves as an intriguing addition to the three well-established classic modes of crystal growth. In exploring electronic growth, Pb(111) films represent a particularly compelling example, not only because their stability exhibits unusually strong quantum oscillations but also because their physical and chemical properties can be tuned with great precision by controlling the film thickness or the chemical composition. Recent advances and the perpectives in this active area of film growth will be reviewed, with results from both theoretical and experimental studies. Historical ReviewLow-dimensional materials have been an important platform for the discovery of novel quantum phenomena, such as the quantized conductance and quantum Hall effects in semiconductor heterostructures [1] and giant magneto-resistance in metallic magnetic superlattices [2]. In these examples, fabrication of the low-dimensional medium was accomplished via classical thin film growth; yet the emerging properties are clearly quantum mechanical in nature. More recently, it has been shown that the size quantization of itinerant electrons in an ultrathin metal film also plays a decisive role in the early formation stages and kinetic stability of the films [3][4][5][6][7][8][9].

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Quantum Size Effects in the Growth, Coarsening, and Properties of Ultra-thin Metal Films and Related Nanostructures

Cited by 39 publications

References 65 publications

First-principles studies of hydrogen interaction with ultrathin Mg and Mg-based alloy films

First-principles studies of hydrogen interaction with ultrathin Mg and Mg-based alloy films

Influence of interface reconstruction on the formation and superconductive properties of metastable Pb-Ga alloy films

Quantum Size Effects in the Growth and Properties of Ultrathin Metal Films, Alloys, and Related Low-Dimensional Structures

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