Electronic properties and superconductivity of amorphous Si_1‐xAu_x alloys near the metal‐insulator transition

Abstract

Abstract. We report on specific-heat and resistivity measurements on quench-condensed Si, -,Au, films for 0.1 1 GxGO.36 in the temperature range 0.35 K G T G 6 K. A distinct increase of the specificheat derived electronic density of states at the Fermi level is observed at xb = 0.2, i.e, in the vicinity of the metal-insulator transition occurring for our samples at X, = 0.16. This suggests a different type of bonding between Au and Si for x<xb and x>xb. While resistive transitions to superconductivity are observed for ~2 0 . 2 1 , the absence of a specific-heat anomaly at the transition points to filamentary superconductivity except for x = 0.35 where a sizable anomaly is seen. The difference in various electronic properties between differently prepared samples of these metastable alloys, in particular the influence of different preparation and annealing temperatures is emphasized. It is suggested that these differences are caused by incipient phase separation in the room-temperature prepared samples.

Metal–insulator transition in amorphous alloys

“…This subject has been investigated so intensively that it is impossible to give here a complete survey of all related studies of structure and transport properties of amorphous alloys in the vicinity of the MIT. Thus the following selection, listed according to the alloys investigated, contains merely the more important publications on low-temperature transport and, in some cases, structure: Ge-Al [27], Ge-Au [28][29][30], Ge-Co [31], Ge-Cu [32], Ge-Cr [31,[33][34][35], Ge-Fe [31,[36][37][38][39][40], Ge-Mn [31], Ge-Mo [40,41], Ge-Ni [31], Si-Au [42][43][44][45][46][47], Si-Cr [35,[48][49][50][51][52][53][54][55][56][57], Si-Fe [38,58,59], Si-Gd [60,61], Si-Mn [58,[62][63][64], Si-Nb …”

Metal–insulator transition in amorphous alloys

“…This subject has been investigated so intensively that it is impossible to give here a complete survey of all related studies of structure and transport properties of amorphous alloys in the vicinity of the MIT. Thus the following selection, listed according to the alloys investigated, contains merely the more important publications on low-temperature transport and, in some cases, structure: Ge-Al [27], Ge-Au [28][29][30], Ge-Co [31], Ge-Cu [32], Ge-Cr [31,[33][34][35], GeFe [31,[36][37][38][39][40], Ge-Mn [31], Ge-Mo [40,41], Ge-Ni [31], Si-Au [42][43][44][45][46][47], Si-Cr [35,[48][49][50][51][52][53][54][55][56][57], Si-Fe [38,58,59], Si-Gd [60,61], Si-Mn [58,[62][63][64], Si-Nb …”