Au–Ge bonding on a uniformly Au‐covered Ge(001) surface

Popescu, D.; Husanu, Marius-Adrian

doi:10.1002/pssr.201307029

Cited by 12 publications

(9 citation statements)

References 11 publications

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“…Similar findings may be inferred also from the Ge 2p spectra. Therefore, although the LEED pattern is similar, it may happen that the orientation of the dimers and their charge state is modified in the case of MnGe(001) with respect to the case of clean Ge(001), as was evidenced also for Au/Ge(001) [26,27]. This result is in line with the STM observations from Figure 2b, namely the different interatomic distance obtained for the surface dimers.…”

Section: Resultssupporting

confidence: 84%

“…Additional proof is as follows: when Au is deposited on a similar Ge(001) wafer as used in the actual experiments at relatively low temperature, a band bending of the Ge 3d “bulk” component is obtained by ~0.15 eV towards lower binding energies [26], as expected from the difference of workfunctions between Au (5.1–5.3 eV) and Ge (5.0 eV) [50]. When Au is deposited at elevated temperature (750 K), the band bending reverses its sign: it yields about 0.1 eV towards higher binding energies [27], close to the actual case. The origin of this reversed band bending (irrespective of the workfunction of the metal used) suggests the presence of defects introduced by the metal under the Ge(001) surface, which act as shallow acceptors [51].…”

Section: Resultsmentioning

confidence: 99%

“…in a vacuum kept in the low 10 −9 mbar range) [24,26,27]. Clear (2 × 1)–(1 × 2) LEED were obtained, as seen in Figure 1.…”

Section: Methodsmentioning

confidence: 91%

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Room Temperature Ferromagnetic Mn:Ge(001)

et al. 2013

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We report the synthesis of a room temperature ferromagnetic Mn-Ge system obtained by simple deposition of manganese on Ge(001), heated at relatively high temperature (starting with 250 °C). The samples were characterized by low energy electron diffraction (LEED), scanning tunneling microscopy (STM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), superconducting quantum interference device (SQUID), and magneto-optical Kerr effect (MOKE). Samples deposited at relatively elevated temperature (350 °C) exhibited the formation of ~5–8 nm diameter Mn5Ge3 and Mn11Ge8 agglomerates by HRTEM, while XPS identified at least two Mn-containing phases: the agglomerates, together with a Ge-rich MnGe~2.5 phase, or manganese diluted into the Ge(001) crystal. LEED revealed the persistence of long range order after a relatively high amount of Mn (100 nm) deposited on the single crystal substrate. STM probed the existence of dimer rows on the surface, slightly elongated as compared with Ge–Ge dimers on Ge(001). The films exhibited a clear ferromagnetism at room temperature, opening the possibility of forming a magnetic phase behind a nearly ideally terminated Ge surface, which could find applications in integration of magnetic functionalities on semiconductor bases. SQUID probed the co-existence of a superparamagnetic phase, with one phase which may be attributed to a diluted magnetic semiconductor. The hypothesis that the room temperature ferromagnetic phase might be the one with manganese diluted into the Ge crystal is formulated and discussed.

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Section: Resultssupporting

confidence: 84%

Section: Resultsmentioning

confidence: 99%

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Room Temperature Ferromagnetic Mn:Ge(001)

et al. 2013

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“…A final observation addresses the stability of the interface formation as deduced from DFT calculations . Au lattice constant

a_{A u} = 4.078

Å is close to that of BTO strained at the in‐plane STO lattice constant,

a_{S T O} = 3.905

Å. Consequently, one would expect that the epitaxy condition is rather easily fulfilled for Au growth.…”

mentioning

confidence: 72%

Impact on Ferroelectricity and Band Alignment of Gradually Grown Au on BaTiO₃

Popescu

Husanu

Chirilă

et al. 2019

Physica Rapid Research Ltrs

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The competition between interface barrier in the Schottky-Mott limit and polarization driven mechanism is established during gradual formation of metal (Au)ferroelectric (BaTiO 3 ) interface. X-ray photoelectron spectroscopy provides core level energies and valence band positions in the contact region, to monitor the band alignment from the very first stages of metal deposition on BaTiO 3 . The band bending at metal/ferroelectric (FE) interface is extracted from the shift of core levels (Ba 3d, Ti 2p) as a function of the metal thickness. It is shown that the interface band alignment mechanism involves a well-defined polarization orientation washing out the bending expected from the work function difference. The sudden modification of the binding energies within ferroelectric at the first 2 ÅAu indicates that the ferroelectric compensation mechanism triggered by the metal overlayer initiates already at ultrathin top layer, while subsequent growth contributes only at a gradual correction of the potential in the FE. The emerging picture is confirmed in first-principle calculation indicating the preferences of Au to grow preferentially to different terminated regions and to stabilize distinct ferroelectric polarization.Ferroelectric materials exhibit a spontaneous polarization, which can be reversed by applying a voltage exceeding the coercive field. [1] They are used in a wide number of applications such as sensors and actuators, [2,3] in ferroelectric capacitors [4] and nonvolatile memories. [5,6] In most of these applications, the ferroelectric (FE) system is in direct contact with a metal electrode, and the device physics is strongly influenced by the metal-ferroelectric interface. Consequently, understanding the mechanism of metal/FE interface formation is of central importance in device design. Ferroelectric thin films may present a particular single-domain ferroelectric state with the polarization perpendicular to the film, which is connected to the existence of free charge carriers into the film. [7] Electrons and holes from the ferroelectric thin film may then be transferred by the internal field (P=e, where P ¼ polarization perpendicular to the surface of the FE, e ¼ e 0 e r ¼ dielectric permittivity of the FE)

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“…139,172,176,177 It was even shown that for 1 ML Au deposition replacing all surface Ge-dimers by Au-dimers leads to a very stable configuration, which agrees very well with the experimental observation of the formation of 3D Au islands under high deposition amounts. 172,178 It also explains why no β-terraces are observed for the Au-deposited systems.…”

Section: Simple Models For Au Nanowiresmentioning

confidence: 95%

Modeling 1D structures on semiconductor surfaces: synergy of theory and experiment

Vanpoucke

2014

J. Phys.: Condens. Matter

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Atomic scale nanowires attract enormous interest in a wide range of fields. On the one hand, due to their quasi-one-dimensional nature, they can act as a experimental testbed for exotic physics: Peierls instability, charge density waves, and Luttinger liquid behavior. On the other hand, due to their small size, they are of interest for future device applications in the micro-electronics industry, but also for applications regarding molecular electronics. This versatile nature makes them interesting systems to produce and study, but their size and growth conditions push both experimental production and theoretical modeling to their limits. In this review, modeling of atomic scale nanowires on semiconductor surfaces is discussed focusing on the interplay between theory and experiment. The current state of modeling efforts on Pt-and Au-induced nanowires on Ge (001) is presented, indicating their similarities and differences. Recently discovered nanowire systems (Ir, Co, Sr) on the Ge(001) surface are also touched upon. The importance of scanning tunneling microscopy as a tool for direct comparison of theoretical and experimental data is shown, as is the power of density functional theory as an atomistic simulation approach. It becomes clear that complementary strengths of theoretical and experimental investigations are required for successful modeling of the atomistic nanowires, due to their complexity.

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Au–Ge bonding on a uniformly Au‐covered Ge(001) surface

Cited by 12 publications

References 11 publications

Room Temperature Ferromagnetic Mn:Ge(001)

Room Temperature Ferromagnetic Mn:Ge(001)

Impact on Ferroelectricity and Band Alignment of Gradually Grown Au on BaTiO₃

Modeling 1D structures on semiconductor surfaces: synergy of theory and experiment

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Au–Ge bonding on a uniformly Au‐covered Ge(001) surface

Cited by 12 publications

References 11 publications

Room Temperature Ferromagnetic Mn:Ge(001)

Room Temperature Ferromagnetic Mn:Ge(001)

Impact on Ferroelectricity and Band Alignment of Gradually Grown Au on BaTiO3

Modeling 1D structures on semiconductor surfaces: synergy of theory and experiment

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Impact on Ferroelectricity and Band Alignment of Gradually Grown Au on BaTiO₃