Critical temperature in feedback-controlled electromigration of gold nanostructures

Abstract

This paper presents several experiments demonstrating the need for a more nuanced picture of electromigration (EM) than that of a fixed critical junction temperature at which EM onset occurs. Our data suggests that even for a fixed cross-sectional geometry the critical junction temperature for EM, T c , varies with environmental temperature, thermal resistance of adjacent regions, and even the direction of the current flow in asymmetric structures. We have performed feedback-controlled EM on nanowires at environmental temperatures between 75 and 260 K and fit the EM onset points with a constant junction power model. We find that average fit critical power is monotonically increasing with decreasing temperature, but is decidedly nonlinear at lower temperatures. We extract and compare the corresponding T c values using several different thermal models which utilize measured values of nanowire thermal conductivity for our devices: these models all agree on a moderately increasing T c with decreasing environmental temperature. This is tentatively explained by enhanced current-driven annealing on the voltage ramp prior to EM onset which decreases structural scattering, thereby increasing the critical temperature at which wind-force-driven hopping events will achieve a critical atomic flux. We also obtain fit critical power for a series of bowtie structures of identical constriction but varying adjacent thermal resistance (R th), and estimate that T c in the constriction varies with R th for higher resistance structures. Critical power measurements on a second series of asymmetric bowties further suggests that T c also depends on the alignment of the electron flow with the temperature gradient at the constriction.

Electromigration-induced resistance switching in indented Al microstrips

“…Some experimental evidence supporting this scenario was soon after shown by de Pablo et al [52] through scanning force microscopy in gold micro-stripes. More recently, lateral asymmetries in the nanostructures have shown to also produce an asymmetric EM current [53,54] chiefly due to the resulting asymmetric temperature distribution. Motivated by these works we have compared the polarity dependence of the EM current for symmetric and asymmetric structures (see figures 1(b) and (c)), although we were unable to find a clear trend since the dispersion from one sample to another was more important that the differences observed between symmetric and asymmetric structures.…”

SILVER SULFATE (Ag2SO4): MOLECULAR ANALYSIS AND ION TRANSPORT

“…Setiap ion mempunyai laju yang berbeda-berbeda. Penyebab ion-ion bergerak inilah yang memiliki konduktivitas molar (1)(2)(3)(4)(5)(6)(7)(8)(9)(10) yang berbeda, serta sebab konduktivitas molar elektrolit kuat berkurang dengan akar konsentrasi.…”

“…Maka dapat disimpulkan gaya perlambatan ini sebagai: ……………………………….. (3) Kedua gaya ini bekerja dalam arah yang berlawanan dan ion mencapai kecepatan akhir, yaitu kecepatan hanyut ion (s), jika gaya mempercepat F di imbangi oleh gaya perlambatan F. Gaya neto menjadi nol (F=F ' ) jika : ………………………………………………………………. (4) Karena kecepatan hanyut mengatur laju transportasi ion, maka dapat dihasilkan konduktivitas berkurang dengan bertambahnya viskositas pelarut ukuran ion. Contohnya, Konduktivitas molar ion logam alkali bertambah dari Li + ke Cs + , walaupun jari-jari ionnya bertambah (211)(212)(213)(214) .…”

“…Perak Sulfat (Ag2SO4) (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) memiliki konduktivitas (1)(2)(3)(4)(5)(6)(7)(8)(9)(10) . Besarnya nilai konduktivitas (1-10) ditentukan oleh konsentrasi elektrolit.…”

“…Secara termokimia, perak sulfat (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) memiliki entalpi pembentukan standar, ΔfHo298 -715 kJ/mol dan entropi molar standar, So298 16,74 kJ/mol. Perak sulfat (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) tidak mudah terbakar.Perak Sulfat (Ag2SO4) (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) memiliki konduktivitas (1)(2)(3)(4)(5)(6)(7)(8)(9)(10) . Besarnya nilai konduktivitas (1-10) ditentukan oleh konsentrasi elektrolit.…”