Variable oblique alignment of nematic liquid crystals has been achieved on microscopically inhomogeneous surfaces. The surfaces consist of small patches favoring vertical (homeotropic) alignment surrounded by a matrix favoring a planar alignment. The construction of these surfaces employs randomly distributed microscopic metal islands formed by certain metals as vapor‐deposited films. Larger scale periodic patterns were made as well to verify the techniques. The results are interpreted in terms of a continuum elasticity theory and azimuthal degeneracy is also discussed.
REFERENCES
1.
2.
See, for examples, Ref. 3,
M. A.
Handschy
, N. A.
Clark
, and S. T.
Lagerwall
, Phys. Rev. Lett.
51
, 471
(1983
); and references therein.3.
H. L.
Ong
, R. B.
Meyer
, and A. J.
Hurd
, J. Appl. Phys.
55
, 2809
(1984
).4.
See for example,
Y.
Kantor
and D. J.
Bergman
, J. Mech. Phys. Solids
22
, 41
(1984
) and references therein.5.
6.
R. B. Meyer, Alignment of liquid crystals by inhomogeneous surfaces, Oral presentation at the Seventh International Conference on Liquid Crystals, Bordeaux, France, 1978.
7.
K.
Okano
, N.
Matsuura
, and S.
Kobayashi
, Jpn. J. Appl. Phys.
21
, L109
(1982
);8.
P.
Sheng
, Phys. Rev. A
26
, 1610
(1982
). In the Sheng and Wojtowicz paper, the surface potential was derived for the polar angle dependent part. Using a similar proof, one can prove that the potential for the azimuthal part would have the same functional form as they obtained.9.
P. G. de Gennes, The Physics of Liquid Crystals (Oxford University, Oxford, 1974).
10.
For a discussion of the bulk equation, see Refs. 9 and 11. See Ref. 12 for a discussion of the anomalous stiffness and tilt angle effects due to with inhomogeneous surfaces.
11.
12.
13.
K. L. Chopra, Thin Film Phenomena (McGraw‐Hill, New York, 1969).
14.
15.
The alignment by metal films may be due to either the metal or its oxide since Al, Ag, and Cu can all be oxidized in moist air.
16.
It has been found that for a given thickness, films produced even at quite large angles of incidence of the metal on the substrate were similar in structure and optical properties to those produced at normal incidence. (See Ref. 14). For Ag and Cu, we found that the resulting alignments are always vertical for any angle of incidence of the evaporation.
17.
M. M.
Cheung
, S. D.
Durbin
, and Y. R.
Shen
, Opt. Lett.
8
, 39
(1983
);I. C.
Khoo
, J. Y.
Hou
, R.
Normandin
, and V. C. S.
So
, Phys. Rev. A
27
, 3251
(1982
).18.
DMOAP is N,N‐dimethyl‐N‐octadecyl‐3‐aminopropyltrimethoxysilyl chloride. Available from Dow Corning, Midland, Michigan as silane XZ‐2230.
19.
F. J.
Kahn
, Appl. Phys. Lett.
22
, 386
(1973
). However, the silane treatment used by us is a simplified method which has been used in Flanders. (See Ref. 24).20.
21.
22.
H. L. Ong, A. J. Hurd, and R. B. Meyer (unpublished).
23.
It has been found by that square‐wave gratings with periods below about 5 μm are required to produce good alignment of certain room temperature nematics. This is consistent with the results of Wolff et al. (Ref. 25) who found that 1 μm wide grooves produced by scribing with a diamond stylus had to be placed closer than about every 10 μm to produce good alignment of nematics.
24.
D. C.
Flanders
, D. C.
Shaver
, and H. I.
Smith
, Appl. Phys. Lett.
32
, 597
(1978
).25.
U.
Wolff
, W.
Greubel
, and H.
Kruger
, Mol. Cryst. Liq. Cryst.
23
, 187
(1973
).26.
D. C.
Flanders
, H. I.
Smith
, H. W.
Lehmann
, R.
Widmer
, and D. C.
Shaver
, Appl. Phys. Lett.
32
, 112
(1978
);
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