Aluminum Nitride Tunnel Barrier Formation with Low-Energy Nitrogen Ion Beams

We report the use of low-energy nitrogen ion beams to form ultra-thin ( x to act as tunnel barriers in Nb/Al–AlN x /Nb Josephson junctions. We fabricated reproducible, high-quality devices with independent control of the ion energy and dose, enabling exploration of a wide parameter space. Critical current density J c ranged from 550 to 9400 A/cm 2 with subgap-to-normal resistance ratios from 50 to 12.6. The spatial variation of ion-current density was roughly correlated with J c over a large-area on a Si substrate. The junctions were stable on annealing up to temperatures of at least 200 °C. This technique could be applied to form other metal nitrides at room temperature for device applications where a high degree of control is desired.

[1]  Shinya Hasuo,et al.  Nb Josephson junction with an AlNx barrier made by plasma nitridation , 1992 .

[2]  L. DeLouise,et al.  Adsorption and desorption of no from Rh{111} and Rh{331} surfaces , 1985 .

[3]  Robert A. Buhrman,et al.  High‐quality submicron niobium tunnel junctions with reactive‐ion‐beam oxidation , 1980 .

[4]  J. Greiner.  Josephson Tunneling Barriers by rf Sputter Etching in an Oxygen Plasma , 1971 .

[5]  T. Zijlstra,et al.  Analysis of the fabrication process of Nb/Al-AlN/sub x//Nb tunnel junctions with low R/sub n/A values for SIS mixers , 2003 .

[6]  A. Kleinsasser.  Influence of beam energy, flux, and composition on junction parameters in ion beam tunnel barrier processing , 1985 .

[7]  Henry G. Leduc,et al.  Fabrication of Nb/Al-N/sub x//NbTiN junctions for SIS mixer applications , 2001 .

[8]  J. Pankove,et al.  Epitaxially grown AlN and its optical band gap , 1973 .

[9]  Sergey V. Shitov,et al.  High quality Nb-based tunnel junctions for high frequency and digital applications , 2003 .

[10]  J. Rabalais,et al.  Reactions of homonuclear diatomic ions with metal surfaces. II. Nitridation of Al, Cu, Mo, and Ni by N+2 beams in the low kinetic energy‐near threshold region , 1982 .

[11]  W. H. Mallison,et al.  Nb/AlN/Nb Josephson junctions with high critical current density , 1995, IEEE Transactions on Applied Superconductivity.

[12]  Hong-Gyu Kang,et al.  Silicon nitride formation by low energy N+ and N+2 ion beams , 1992 .

[13]  Electrical transients in the ion-beam-induced nitridation of silicon , 2001 .

[14]  H. D. Hagstrum.  Studies of Adsorbate Electronic Structure Using Ion Neutralization and Photoemission Spectroscopies , 1978 .

[15]  Jonas Zmuidzinas,et al.  Very High Current Density Nb/AlN/Nb Tunnel Junctions for Low-Noise Submillimeter Mixers , 2000 .

[16]  Y. Uzawa,et al.  NbN/AlN/NbN tunnel junctions fabricated at ambient substrate temperature , 1995, IEEE Transactions on Applied Superconductivity.

[17]  L. Fiermans,et al.  Electron and Ion Spectroscopy of Solids , 1978 .

[18]  Fabrication of wide-IF 200-300 GHz superconductor-insulator-superconductor mixers with suspended metal beam leads formed on silicon-on-insulator , 2004 .

[19]  G. Carter,et al.  The interaction of low energy ion beams with surfaces , 1981 .