Temperature evolution of multiple tunnel junction devices made with disordered two-dimensional arrays of metallic islands

Abstract

The temperature behavior of multiple tunnel junction (MTJ) devices made with sub-5-nm gold islands is investigated. A smooth decrease of the Coulomb gap with increasing temperatures is observed. The critical temperature beyond which the Coulomb blockade effect is suppressed is found to change as a function both of the average size of the islands and of the size of the two-dimensional (2D) array of islands forming the MTJ. This latter property is attributed to the role of disorder in the 2D array. Results are compared with Monte Carlo simulations of current transport through highly disordered 2D arrays which reproduce the experimental evolution of the Coulomb gap with temperature.

Temperature behavior of multiple tunnel junction devices based on disordered dot arrays

“…[2][3][4][5][6][7] In order to retain this current blockade effect up to high temperature, the charging energy E c ϭe 2 /2C, which is requested to allow an extra electron to flow through the single-electron device, must be larger than the thermal fluctuations k B T, with C the device capacitance, k B the Boltzmann constant, and T the temperature; Ϫe is the electrical charge of the electron (eϾ0).…”

Fabrication of MOS-integrated metallic single electron memories

“…The factors of merit of MTJs for memory application are i) a total tunnel resistance in the M• range in order that the writing time related to the speed at which electrons can pass through the MTJ remain in the ns regime, and ii) a clear conservation of a Coulomb gap at operating temperature, which depends on the number, size and average charging energy of the islands forming the MTJ array. An experimental study of the temperature dependance of our disordered 2D MTJ arrays, supported by Monte Carlo simulations [5], showed that lateral patterning of the 2D arrays made the devices more robust against temperature. Figure 3 shows typical currentvoltage characteristics obtained on our 2D mxn Au MTJ arrays.…”

“…Above a critical temperature, slightly higher than 100 K, the gap is destroyed and a conductance can be measured at low voltage [5]. The 1 V Coulomb gap obtained for the MTJ at low temperature should enable high temperature operation of the LSEM, as well as a modulation of the MOS current by more than 3 decades between the "0" and "1" states.…”

“…Although fully compatible with CMOS technology, this device is limited to low temperature operation (4.2 K). Alternatively, granular film deposition can be used to produce MTJs working at higher temperatures [4][5][6]. MTJs made of 2D arrays of disordered sub-5 nm metal islands, exhibiting reproducible Coulomb blockade behaviour at high temperature (>100 K), have been fabricated and characterized [5].…”

“…Alternatively, granular film deposition can be used to produce MTJs working at higher temperatures [4][5][6]. MTJs made of 2D arrays of disordered sub-5 nm metal islands, exhibiting reproducible Coulomb blockade behaviour at high temperature (>100 K), have been fabricated and characterized [5]. In this work we consider the next step towards the fabrication of a lateral single electron memory (LSEM): the integration of a metallic MTJ and a memory node (MN) on a Si metal oxide semiconductor field effect transistor (MOS).…”