The Niemeyer–Dolan technique, also called the Dolan technique, angular evaporation, or the shadow evaporation technique, is a
thin-film lithographic
Lithography () is a planographic method of printing originally based on the immiscibility of oil and water. The printing is from a stone (lithographic limestone) or a metal plate with a smooth surface. It was invented in 1796 by the German ...
method to create
nanometer
330px, Different lengths as in respect to the Molecule">molecular scale.
The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm), or nanometer (American spelling
Despite the va ...
-sized overlapping structures.
This technique uses an evaporation mask that is suspended above the
substrate
Substrate may refer to:
Physical layers
*Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached
** Substrate (aquatic environment), the earthy material that exi ...
(see figure). The evaporation mask can be formed from two or more layers of
resist
A resist, used in many areas of manufacturing and art, is something that is added to parts of an object to create a pattern by protecting these parts from being affected by a subsequent stage in the process. Often the resist is then removed.
For ...
, to allow creation of the extreme undercut needed. Depending on the evaporation angle, the shadow image of the mask is projected onto different positions on the substrate. By carefully choosing the angle for each material to be deposited, adjacent openings in the mask can be projected onto the same spot, creating an overlay of two thin films with a well-defined geometry.
Efforts to create multilayered structures are complicated by a need to align each layer with those below it; as all openings are on the same mask, shadow evaporation reduces this need by being self-aligning.
Additionally, this allows the substrate to be kept under high vacuum, as there is no need to increase pressure to switch between multiple masks. Due to its downsides, including restrictions on feature density from excess evaporated material, shadow evaporation is generally only suitable for very low scale integration.
Usage
The Niemeyer–Dolan technique is used to create multi-layer
thin-film electronic nanostructures such as
quantum dots
Quantum dots (QDs) or semiconductor nanocrystals are semiconductor particles a few nanometres in size with optical and electronic properties that differ from those of larger particles via quantum mechanical effects. They are a central topic i ...
and
tunnel junctions.
References
{{DEFAULTSORT:Niemeyer-Dolan Technique
Nanoelectronics