Microkelvin physics

Pickett, G. R.

doi:10.1088/0034-4885/51/10/001

Cited by 59 publications

(66 citation statements)

References 45 publications

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“…29 We used norm-conserving scalar-relativistic Troullier-Martins pseudopotentials 30,31 in the Kleinman-Bylander nonlocal form 32 and the exchange-correlation functional of Ceperley and Alder. 33 The electronic states were expanded on a planewave basis set using a kinetic energy cutoff of 20 Ry.…”

Section: Methods Of Calculationmentioning

confidence: 99%

Schottky barrier heights at polar metal/semiconductor interfaces

Berthod

Binggeli

Baldereschi³

2003

Phys. Rev. B

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ZnSe ͑100͒ junctions, and their dependence on the semiconductor chemical composition and surface termination. A model based on linear-response theory is developed, which provides a simple, yet accurate description of the barrier-height variations with the chemical composition of the semiconductor. The larger barrier values found for the anion-terminated surface than for the cation-terminated surface are explained in terms of the screened charge of the polar semiconductor surface and its image charge at the metal surface. Atomic-scale computations show how the classical image charge concept, valid for charges placed at large distances from the metal, extends to distances shorter than the decay length of the metalinduced-gap states.

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Section: Methods Of Calculationmentioning

confidence: 99%

Schottky barrier heights at polar metal/semiconductor interfaces

Berthod

Binggeli

Baldereschi³

2003

Phys. Rev. B

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“…10,11 Another approach-pursued by our Basel group 12 -is to use nuclear cooling 6-8 on the sample wires, with the potential to advance well into the microkelvin range. Thermometry in this regime [6][7][8] typically faces similar challenges as cooling nanostructures and is ideally integrated on-sample. Among numerous sensors, 13 Coulomb blockade thermometers 14 (CBTs) are simple to use and self-calibrating yet offer high accuracy, demonstrated down to ∼20 mK.…”

mentioning

confidence: 99%

“…The temperature T Cu of the Cu pieces is obtained using a standard technique: 7,8,12 after demagnetization, we apply power on heaters mounted on some of the NRs and evaluate the warm-up time-dependence T Cu (t) measured with Lanthanum Cerium Magnesium Nitrate (LCMN) thermometers above 2 mK. This allows us to determine both the temperature T Cu of the Cu-NRs after demagnetization as well as a small field-offset.…”

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confidence: 99%

Metallic Coulomb blockade thermometry down to 10 mK and below

Casparis

Meschke²,

Maradan³

et al. 2012

Review of Scientific Instruments

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We present an improved nuclear refrigerator reaching 0.3 mK, aimed at microkelvin nanoelectronic experiments, and use it to investigate metallic Coulomb blockade thermometers (CBTs) with various resistances R. The high-R devices cool to slightly lower T , consistent with better isolation from the noise environment, and exhibit electron-phonon cooling ∝ T 5 and a residual heat-leak of 40 aW. In contrast, the low-R CBTs display cooling with a clearly weaker T -dependence, deviating from the electron-phonon mechanism. The CBTs agree excellently with the refrigerator temperature above 20 mK and reach a minimum-T of 7.5 ± 0.2 mK.

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“…The AlN/GaN/InN interfaces are all of type I, while the Al 0.5 Ga 0.5 N/AlN zinc-blende ͑001͒ interface is found to be of type II. Finally, we studied the GaN/AlN wurtzite interface, where qualitatively new features, namely pyroelectric and piezoelectric effects, appear due to the low symmetry of the wurtzite lattice.The standard ab initio plane-wave pseudopotential method [8][9][10] was employed in the calculations. The energy cutoff for the plane-wave expansion was 50 Ry to ensure convergence of the nitrogen pseudopotential.…”

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confidence: 99%

Strain effects on the interface properties of nitride semiconductors

1997

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An ab initio study of nitride-based heteroepitaxial interfaces that uses norm-conserving pseudopotentials and explicitly treats the strain due to lattice mismatch is presented. Strain effects on the band offsets range from 20% to 40%. The AlN/GaN/InN interfaces ͑with AlN in-plane lattice constant͒ are all of type I, while the Al 0.5 Ga 0.5 N/AlN zinc-blende ͑001͒ interface is of type II. Further, the bulk polarizations in wurtzite AlN and GaN are Ϫ1.2 and Ϫ0.45 C/cm 2 , respectively, and the interface contribution to the polarization in the GaN/AlN wurtzite multiquantum-well is small. ͓S0163-1829͑97͒52912-2͔With the recent demonstration of stimulated emission in the blue region of the spectrum from a nitride-based multiquantum-well structure, 1 interest in the nitride-based semiconductors has burgeoned. This discovery has served to underscore the very attractive properties of the nitride-based materials, which include a wide band gap and the ability to form a continuous range of solutions of GaN, AlN, and InN, materials that have very different band gaps. This latter property makes possible the engineering of band gaps that span the range from the deep ultraviolet to the visible. Not surprisingly the potential technological importance of these materials has elicited the interest of a number of theoretical groups. [3][4][5][6][7] In spite of this, the strained interfaces of these lattice mismatched materials have not been studied. We find that strain effects are significant, inducing changes of 20% to 40% in the value of the band offset and that these changes increase with decreasing in-plane lattice parameter. The AlN/GaN/InN interfaces are all of type I, while the Al 0.5 Ga 0.5 N/AlN zinc-blende ͑001͒ interface is found to be of type II. Finally, we studied the GaN/AlN wurtzite interface, where qualitatively new features, namely pyroelectric and piezoelectric effects, appear due to the low symmetry of the wurtzite lattice.The standard ab initio plane-wave pseudopotential method [8][9][10] was employed in the calculations. The energy cutoff for the plane-wave expansion was 50 Ry to ensure convergence of the nitrogen pseudopotential. We used the equivalent of ten k points for bulk and superlattice calculations in the zinc-blende structure 11 and six k points for calculations of the wurtzite structure.12 Convergence both in the size of the plane-wave basis and in the number of special points has been carefully checked. The Perdew-Zunger parametrization 13 of the Ceperley-Alder form 14 of the exchange-correlation energy was used. For interface calculations, we employed 4ϩ4 superlattices ͑16 atoms͒ along the ͑001͒ and ͑0001͒ directions. Nonlocal, norm-conserving pseudopotentials [15][16][17] were included using the KleinmanBylander approach.18 For nitrogen, we used a neutral configuration as the atomic reference for all states.In pseudopotentials where d electrons are treated as core electrons, experience with II-VI semiconductors 19 has shown that the inclusion of the nonlinear core correction 20 results in a subst...

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Microkelvin physics

Cited by 59 publications

References 45 publications

Schottky barrier heights at polar metal/semiconductor interfaces

Schottky barrier heights at polar metal/semiconductor interfaces

Metallic Coulomb blockade thermometry down to 10 mK and below

Strain effects on the interface properties of nitride semiconductors

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