Superconducting State in a Gallium-Doped Germanium Layer at Low Temperatures

Herrmannsdörfer, T.; Heera, V.; Ignatchik, O.; Uhlarz, M.; Mücklich, A.; Posselt, M.; Reuther, H.; Schmidt, Bertram; Heinig, K. H.; Skorupa, W.; Voelskow, M.; Wündisch, C.; Skrotzki, R.; Helm, M.; Wosnitza, J.

doi:10.1103/physrevlett.102.217003

Cited by 86 publications

(74 citation statements)

References 24 publications

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“…If we extrapolate the linear dependence for T → 0, we find B c2|| ≈ 0.8 T for the sample annealed at 60 J/cm 2 . A linear dependence of B c2|| down to 0.1 T c has been revealed within our previous investigations of Ge:Ga [5]. The theory of Werthamer, Helfand, and Hohenberg describes B c2 (T) for superconductors in the dirty limit, i.e., where the Ginzburg-Landau coherence length is restricted by short electronic mean-free paths [28][29][30].…”

Section: Superconducting Propertiesmentioning

confidence: 99%

“…In our previous investigations, flash-lamp or rapid thermal annealing (RTA) were accompanied by an emerging dopant diffusion and, finally, a loss of dopant atoms through out-diffusion at higher temperatures [5,8]. As a consequence, superconductivity has been excluded or at least shifted to lower temperatures in the samples where a loss of dopants has been observed.…”

Section: Preparation Methodsmentioning

confidence: 99%

“…To prevent surface degradation during implantation, an additional 30 nm SiO 2 capping has been sputtered on top of the wafers. Implantation has been carried out with 100 keV Ga + ions at a total dose of 2·10 16 cm -2 , equal to our previous investigations [5,8]. Though, further samples with a lower dose, 0.6·10 16 cm -2 , have been prepared for comparison.…”

Section: Measurement Techniquementioning

confidence: 99%

“…Replacing high-pressure high-temperature synthesis by chemical vapor deposition successfully increased T c of BDD from around 4 to more than 7 K [3,6]. Alternatively, improved gas-immersion laser doping (rising T c from 0.4 to 0.6 K in Si:B) [4,7] and enhanced ion implantation accompanied by flash-lamp or rapid thermal annealing (rising T c from 0.5 to 1.2 K in Ge:Ga) [5,8] have been demonstrated.…”

Section: Introductionmentioning

confidence: 99%

“…Highly doped diamond [3], silicon [4], and germanium [5] -classic group-IV semiconductors -surprisingly turned out to be low-temperature superconductors. However, to achieve this, doping concentrations beyond the metal-to-insulator transition (MIT) had to be incorporated.…”

Section: Introductionmentioning

confidence: 99%

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The impact of heavy Ga doping on superconductivity in germanium

Skrotzki

Herrmannsdörfer

Heera

et al. 2011

Low Temperature Physics

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We report new experimental results on how superconductivity in gallium-doped germanium (Ge:Ga) is influenced by hole concentration and microstructure. Ion implantation and subsequent flash-lamp annealing at various temperatures have been utilized to prepare highly p-doped thin films consisting of nanocrystalline and epitaxially grown sublayers with Ga-peak concentrations of up to 8 at.%. Successive structural investigations were carried out by means of Rutherford-backscattering spectrometry in combination with ion channelling, secondaryion-mass spectrometry, and high-resolution cross-sectional transmission electron microscopy. Hole densities of 1.8·10 20 to 5.3·10 20 cm -3 (0.4 to 1.2 at.%) were estimated via Hall-effect measurements revealing that only a fraction of the incorporated gallium has been activated electrically to generate free charge carriers. The coincidence of a sufficiently high hole and Ga concentration is required for the formation of a superconducting condensate. Our data reflect a critical hole concentration of around 0.4 at.%. Higher concentrations lead to an increase of T c from 0.24 to 0.43 K as characterized by electrical-transport measurements. A short mean-free path indicates superconductivity in the dirty limit. In addition, small critical-current densities of max. 20 kA/m 2 point to a large impact of the microstructure.PACS: 74.10.+v Occurrence, potential candidates; 74.78.-w Superconducting films and low-dimensional structures.

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Section: Superconducting Propertiesmentioning

confidence: 99%

Section: Preparation Methodsmentioning

confidence: 99%

Section: Measurement Techniquementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The impact of heavy Ga doping on superconductivity in germanium

Skrotzki

Herrmannsdörfer

Heera

et al. 2011

Low Temperature Physics

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Xenes as an Emerging 2D Monoelemental Family: Fundamental Electrochemistry and Energy Applications

Wang

Kou

et al. 2020

Adv Funct Materials

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As an emerging subclass of 2D materials, Xenes (e.g., borophene, silicene, germanene, stanene, phosphorene, arsenene, antimonene, and bismuthene) consist of one single element and have opened the door for various important applications. Benefiting from their impressive characteristics, including ultrathin folded structure, ultrahigh surface–volume ratio, excellent mechanical strength and flexibility, Xenes are considered as promising electrode materials in the field of electrochemical energy with large capacity, high rate, and high safety. This review provides a comprehensive summary of selected properties, synthetic challenges, and the latest theoretical and experimental advances in the energy‐related applications of Xenes, including Li/Na ion batteries, Li–S batteries, electrocatalysis, and supercapacitors. Finally, the challenges and outlook of this emerging field are discussed.

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Light‐Induced Bipolar‐Resistance Effect Based on Metal–Oxide–Semiconductor Structures of Ti/SiO₂/Si

Wang

2010

Advanced Materials

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Electrical resistance originates from the scattering of electrons and reflects an inherent nature of any given material. The effective manipulation of resistance is an old and fundamental issue and is always an attractive research area for scientists and engineers due to the huge potential for applications. The two methods most commonly used to control resistance are via change of temperature or via the application of an external field. The most successful examples of the two methods may be superconductivity [1][2][3][4][5][6][7] with the zero resistance below a critical temperature and giant magnetoresistance [8][9][10][11][12] (GMR) that can be controlled by the presence of a magnetic field, respectively. Although many resistance effects, such as GMR or superconductivity, have been utilized in a variety of applications, [13][14][15][16][17] including DNA-templating technology, ultranarrow superconducting wires, memory resistance switching, storage technology, and molecular optoelectronic switches, new attempts for the control of resistance are still sought after due to the wide range of applications in many disciplines. In this work, we report the discovery of a new resistance effect in a Ti/SiO 2 /Si metaloxide-semiconductor (MOS) structure. The MOS structures have been extensively studied as solar-cell materials and field-effect transistors for many decades. In recent years there have been reports showing that MOS structures can also be used in some novel applications, such as complementary MOS (CMOS)-compatible immunodetection sensors and high-speed optical modulators. [18][19] However, the MOS serving as a resistance control is new.The experiments were performed in the Ti/SiO 2 /Si structures (Fig. 1a). The polycrystal Ti films (Fig. 1b and c) of varying thickness were fabricated on n-type single crystal Si (111) substrates (20 mm Â 5 mm rectangles, 0.3-mm thickness) by dc sputtering at room temperature. The Si substrate was covered with a thin native 1.2-nm SiO 2 layer that was been confirmed by high-resolution transmission electron microscopy (HRTEM), as shown in Figure 1a. The base pressure of the vacuum system prior to deposition was better than 5.0 Â 10 À5 Pa. A high purity Ti target (60-mm diameter) was used. An argon gas pressure of 0.80 Pa was maintained during deposition. The deposition rates, determined by a stylus profile meter on thick calibration samples, were 0.3 Å s À1 . The samples were scanned with a laser focused into a roughly 50-mm-diameter spot at the surface and without any spurious illumination (e.g., background light) reaching the samples. All the contacts (less than 1 mm in diameter) to the films were formed by alloying indium and showed no measurable rectifying behavior. The samples were measured in air, which may result in the possible oxidation of the Ti layer.Initially we discuss the results for a structure with a Ti thickness of 6.2 nm, which results in the strongest effect for Ti/ SiO 2 /Si. This structure has an initial metal-side resistance of 1.2 MV (R 0 ) over the region o...

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Superconducting State in a Gallium-Doped Germanium Layer at Low Temperatures

Cited by 86 publications

References 24 publications

The impact of heavy Ga doping on superconductivity in germanium

The impact of heavy Ga doping on superconductivity in germanium

Xenes as an Emerging 2D Monoelemental Family: Fundamental Electrochemistry and Energy Applications

Light‐Induced Bipolar‐Resistance Effect Based on Metal–Oxide–Semiconductor Structures of Ti/SiO₂/Si

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Superconducting State in a Gallium-Doped Germanium Layer at Low Temperatures

Cited by 86 publications

References 24 publications

The impact of heavy Ga doping on superconductivity in germanium

The impact of heavy Ga doping on superconductivity in germanium

Xenes as an Emerging 2D Monoelemental Family: Fundamental Electrochemistry and Energy Applications

Light‐Induced Bipolar‐Resistance Effect Based on Metal–Oxide–Semiconductor Structures of Ti/SiO2/Si

Contact Info

Product

Resources

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Light‐Induced Bipolar‐Resistance Effect Based on Metal–Oxide–Semiconductor Structures of Ti/SiO₂/Si