Visible effects of static electric field on physical vapor growth of lead phthalocyanine crystals

Abstract

To elucidate the effects of a static electric field on the crystal growth of a molecule with both a molecular dipole and a quadrupole moment, we performed physical vapor growth of monoclinic lead phthalocyanine (PbPc) crystals under quasithermal equilibrium conditions and observed distinct effects of the applied electric field on the drift motion of the molecules that diffused over the substrate surface. The density of crystals grown on the Au electrode with a high electric potential exceeds the crystal density on both an electrically grounded electrode and a glass substrate surface. In addition, this difference in crystal density increases with applied voltage. This biased distribution of crystal growth is explained by the drift motion of diffusing molecules, which is induced by the interaction of the electric field with molecular dipole and quadrupole moments. However, the long-range oriented growth that is clearly seen in the physical vapor growth with an electric field for copper phthalocyanine is not observed in the crystal growth of PbPc; only a locally oriented growth is observed in the vicinity of the Au electrode. For electric-field-sensitive PbPc, it is difficult to maintain quasithermal equilibrium conditions over a wide area because the distribution of the diffusing molecules varies as a function of the spatially nonuniform electric field, which disturbs the long-range oriented growth.

Molecular Manipulation Technologies Using an Electric Field and Application to Organic Nanoelectronics

“…Figure 3 shows an optical micrograph of PbPc crystals grown under quasithermal equilibrium conditions and a static electric field, from Ref. [35]. The voltage applied to each electrode is indicated in the figure.…”

“…The point in this case is understood by considering the contribution of the molecular dipole and molecular quadrupole moment; a detailed discussion of this is given in Ref. [35]. A higher density of PbPc crystals on the anode than on the cathode is due to the molecular quadrupole moment of PbPc.…”

“…The difference in crystal distribution is clearly dependent on the applied electric field strength. See Ref [35]. for details.…”

In-situ observation of electric-field-induced acceleration in crystal growth of tetrathiafulvalene-tetracyanoquinodimethane

“…23,26 The principles of electric-field-assisted growth observed on a submillimeter scale are also expected to be applicable to nanoscale and molecular scales. For example, we fabricated and demonstrated a self-aligned organic nanochannel transistor [27][28][29] by using the effect of an electric field on tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) crystal growth.…”

“…[1][2][3][4][5][6] In addition, novel and general molecular manipulation technologies are desired for both macroscale and nanoscale applications. Of the many chemical or physical techniques that have been proposed for site and orientation selective growth, the application of external magnetic [7][8][9][10][11][12][13][14][15][16][17][18][19] and electric [20][21][22][23][24][25][26] fields is expected to be widely applicable due to its controllability and universality. However, the effects of external fields are believed to be extremely weak and short ranged.…”