Cu diffusion as an alternative method for nanopatterned CuTCNQ film growth

Abstract

In this paper we show by means of 'in situ' x-ray diffraction studies that CuTCNQ formation from Cu(solid)-TCNQ(solid tetracyanoquinodimethane) goes through Cu diffusion at room temperature. The film quality depends on the TCNQ evaporation rate. At low evaporation rate we get a single phase-I CuTCNQ film very well crystallized and well oriented. The film has a CuTCNQ(0 2 0) orientation. The film is formed by CuTCNQ nanorods of a very homogeneous size. The film homogeneity has also been seen by atomic force microscopy (AFM). The electronic properties of the film have been measured by x-ray photoelectron spectroscopy (XPS) and ultra-violet photoelectron spectroscopy (UPS). Thus, the Cu-diffusion method has arisen as a very simple, clean and efficient method to grow localized CuTCNQ nanorods on Cu, opening up new insights for technological applications.

Organometallic MTCNQ films: a comparative study of CuTCNQ versus AgTCNQ

“…31 In the CuTCNQ films, our X-ray diffraction measurements fitted with an in-plane lattice with the lattice equal to a = 15.83 Å, and b = 15.93 Å and a = b = 901, indicating a lattice slightly lower than the AgTCNQ, corresponding to a smaller metal atom. 16 This structure is compatible with the structure given by Heintz et al 1999, 13 for the phase-I CuTCNQ, if a larger reducible lattice is taken. These authors gave a lattice of a = b = 11.266 Å and a = b = 901 for CuTCNQ.…”

“…This extended diffusion has already been reported elsewhere. 16,23 The electronic properties were studied with an XPS system with a monochromatic Al Ka line, a hemispherical energy analyzer (SPHERA-U7), and an ultraviolet He discharge lamp for ultraviolet photoelectron spectroscopy analysis for the valence band measurements (UPS), and low-energy electron diffraction (LEED) optics. The Al K a line (hn = 1486.7 eV) was used for XPS and the He-I (hn = 21.2 eV) and He-II (hn = 40.8 eV) lines for the UPS measurements.…”

“…This method was used because it produces organometallic MTCNQ films with a very ordered and controlled structure. 16 The initial very well-crystallized and very oriented TCNQ film was grown by evaporating TCNQ molecules under UHV conditions and a controlled low substrate temperature (t = À50 1C). The cool TCNQ film had a monoclinic lattice 29,30 with the TCNQ c-axis lying normal to the substrate surface direction.…”

“…However, it has been proposed that CuTCNQ can be grown by a solid-phase reaction, in which Cu diffuses on to a TCNQ layer deposited on Cu substrates. 16 In the case of growing CuTCNQ by a solid-phase reaction, it is crucial to control the growth mode, structure, and morphology of the former TCNQ film acting as a precursor for the cooper reaction and diffusion. We have shown in previous work 16,17 that the growth of TCNQ films on bare substrates can form very crystalline and oriented films by evaporating TCNQ molecules under UHV conditions at a low evaporation rate and low substrate temperature.…”

“…16 In the case of growing CuTCNQ by a solid-phase reaction, it is crucial to control the growth mode, structure, and morphology of the former TCNQ film acting as a precursor for the cooper reaction and diffusion. We have shown in previous work 16,17 that the growth of TCNQ films on bare substrates can form very crystalline and oriented films by evaporating TCNQ molecules under UHV conditions at a low evaporation rate and low substrate temperature. The crystallinity of the TCNQ layers grown on Cu substrates is of great importance in order to grow well-ordered CuTCNQ films by a solid-phase reaction.…”