Raman study of the mechanism of electrical switching in Cu TCNQ films

Nonvolatile Memory Elements Based on Organic Materials

“…Raman spectroscopy [46] shows that the TCNQ anions in the pristine high-resistance film are replaced by neutral TCNQ molecules in the conductive state. This is consistent with, but does not prove, the mixed-valence conductor (coupled changes in N and l) proposal of Potember.…”

“…In particular, CuTCNQ (TCNQ is the acceptor, tetracyanoquinodimethane) has been very frequently studied. Following the first observations of switching behavior at Johns Hopkins, [45] Raman, [46] frequency dependent impedance, [47] optical, [48] IR, [48] and scanning electron microscopy (SEM) [49] measurements have been made with the goal of clarifying the mechanism. Some recent reports [49,50] start to address issues of device integration and performance.…”

Single‐Crystal Organic Nanowires of Copper–Tetracyanoquinodimethane: Synthesis, Patterning, Characterization, and Device Applications

“…However, some of the principal vibration modes of Cu-TCNQ nanowires-at 1450 cm À1 (CÀCN wing stretch) and 2225 cm À1 (CÀN stretch)-expected on the basis of data reported for TCNQ films, [12] are, in fact, red-shifted by 70 cm À1 and 17 cm À1 , respectively. According to the previous studies, this decrease in the vibrational energy can be attributed to charge transfer between atomic Cu and free TCNQ.…”

“…According to the previous studies, this decrease in the vibrational energy can be attributed to charge transfer between atomic Cu and free TCNQ. [12] Detailed structural characterization of the Cu-TCNQ nanowires was achieved by transmission electron microscopy (TEM, Figure 4). Cu-TCNQ nanowires were grown directly on a copper grid by the same growth procedure as described Figure 4 a show the TEM image of the nanowires protruding from the copper edge of the grid (the lower inset) and the selected-area electron diffraction (SAED) pattern obtained from a collection of the nanowires (the upper inset).…”

Solution growth of metal-organic complex CuTCNQ in small dimension interconnect structures

“…Its resistance change was first reported by Potember et al in 1979 [5], who attributed the switching to a reversible charge transfer between CuTCNQ complex and neutral Cu and TCNQ 0 . In 1982, Kamitsos et al [6] studied the mechanism of electrical switching in CuTCNQ films from in situ Raman spectroscopy: they interpreted the formation of neutral TCNQ 0 under electrical field as a proof of the charge transfer. MIM-type CuTCNQ-based memory elements exhibit a bipolar resistive switching [4,7]: by applying a negative bias to the top electrode (TE) typically made of Al with a grounded bottom electrode (BE), the memory element, initially in a high resistance state (HRS or OFF state), switches into a low resistance state (LRS or ON state), i.e.…”