Content area
Full text
Thin-film electrets have been patterned with trapped charge with submicrometer resolution using a flexible, electrically conductive electrode. A poly(dimethylsiloxane) stamp, patterned in bas-relief and supporting an 80-nanometer-thick gold film, is brought into contact with an 80-nanometer-thick film of poly(methylmethacrylate) supported on n-doped silicon. A voltage pulse between the gold film and the silicon transfers charge at the contact areas between the gold and the polymer electret. Areas as large as 1 square centimeter were patterned with trapped charges at a resolution better than 150 nanometers in less than 20 seconds. This process provides a new method for patterning it suggests possible methods for high-density, charge-based data storage and for high-resolution charge-based printing.
Electrets are materials than can retain trapped electrical charge or polarization (1). Patterns of charge are used in photocopiers (xerography) to develop images with 100 (mu)m resolution (2). Systems that write and read patterns of charge have been explored extensively, because of their potential in rewritable digital data storage (3-5). Current procedures based on scanning probes achieve a writing rate of 100 kbits/s at an areal density of 7 Gbits/cm^sup 2^ (120 run bit size), and achieve a resolution of 100 nin (6, 7). Although this density is about 140 times the areal density of optical compact discs, the writing rate is slow: patterning an area of I cm^sup 2^ requires 24 hours. Here, we describe a method that uses a flexible, micropatterned electrode to pattern an electret thin film in a parallel process by injecting and trapping charges over areas of -1 cm^sup 2^; we call this method electrical microcontact printing (e-(mu)CP). Because the electrode is flexible, it can make sufficiently intimate electrical contact with a solid surface to produce uniform pattern transfer by charging. The resulting patterns were imaged using Kelvin probe force microscopy (KFM) (8). We have used e-(mu)CP to pattern surfaces (> 1 cm^sup 2^) with features ranging from 120 nm to 100 (mu)m in size in less than 20 s; this combination of area feature size, and writing time corresponds to an increase of >10^sup 3^ in writing speed compared to that obtained by a single tip in serial scanning probe methods.
Figure 1 illustrates the procedure. The stamp was poly(dimethylsiloxane) (PDMS), patterned in bas-relief using procedures...