Growth of high-quality large-area MgB₂thin films by reactive evaporation

Abstract

We report a new in-situ reactive deposition thin film growth technique for the production of MgB 2 thin films which offers several advantages over all existing methods and is the first deposition method to enable the production of high-quality MgB 2 films for real-world applications. We ha ve used this growth method, which incorporates a rotating pocket heater, to deposit MgB 2 films on a variety of substrates, including single-crystalline, polycrystalline, metallic, and semiconductor materials up to 4" in diameter. This technique allows growth of double-sided, large-area films in the intermediate temperature range of 400 to 600 °C. These films are clean, well-connected, and consistently display T c values of 38 to 39 K with low resistivity and residual resistivity values. They are also robust and uncommonly stable upon exposure to atmosphere and water.

Evidence for non-s-wave symmetry of theπgap inMgB2from intermodulation distortion measurements

“…The IMD was measured by the stripline-resonator technique, described below, 4,5 employing thin films of MgB 2 that were deposited by the reactive-evaporation method, 20,21 in which boron is deposited in vacuum onto a substrate that rapidly rotates through a region of high-pressure magnesium vapor where the MgB 2 film is formed. This method yields very clean, stable, large-area, double-sided MgB 2 films on a multitude of substrate materials.…”

Measurement of the magnetic penetration depth of a superconducting MgB2thin film with a large intraband diffusivity

“…21,22 The film is epitaxial and shows columnar growth morphology, with the c axis tilted by a few degrees from the normal direction of the substrate. For more details see Ref.…”

Kinetic roughening of magnetic flux penetration in MgB2 thin films

“…We first compare the flux behavior of MgB 2 thin films grown by in situ pulsed laser deposition ͑PLD͒ technique 10 and by a recently developed in situ reactive deposition 11 ͑RD͒ technique. Surprisingly, we do not observe any dendritic instability for the RD samples.…”

“…12 The samples have typical dimensions of 2 ϫ 6 mm 2 , a critical current density of J c =2ϫ 10 6 A / cm 2 at 20 K and a T c = 34 K. RD epitaxial MgB 2 films of 500 nm thickness also were grown on single crystalline Al 2 O 3 -R substrates, using a single step in situ process. 11 The RD samples were cut to dimensions of 2 ϫ 10 mm 2 . These samples show a higher critical temperature T c = 39 K and also a higher critical current density J c =1ϫ 10 6 A / cm 2 at 36 K with respect to the PLD samples.…”

“…These samples show a higher critical temperature T c = 39 K and also a higher critical current density J c =1ϫ 10 6 A / cm 2 at 36 K with respect to the PLD samples. 11 Furthermore, the RD technique produces broad homogeneous MgB 2 films on different substrates which are highly tolerant to moisture or water contact.…”