Regular Paper
Thin Film Deposition of Photoluminescent Silicone Rubber by Pulsed
Laser Deposition
Masayuki OKOSHI1,*, Narumi INOUE1 and Tsugito YAMASHITA2
1

Department of Electrical and Electronic Engineering, National Defense Academy, 1-10-20 Hashirimizu,
Yokosuka, Kanagawa 239-8686, Japan2

Department of Applied Material and Life Science, Kanto Gakuin University, 1-50-1 Mutsuura-Higashi,
Kanazawa-Ku, Yokohama, Kanagawa 236-8501, Japan

Received xxx xx, xxxx; accepted for publication xxx xx, xxxx
Abstract
Silicone ([SiO(CH3)2]n) rubber surface was photochemically modified into photoluminescent property by a faintbeam of 193 nm ArF excimer laser, then the modified surface of silicone rubber was ablated in a vacuum chamber by
the intense ArF excimer laser to deposit thin films of the photoluminescent silicone rubber on a silica glass substrate.
The chemical bonding of the deposited thin films was almost identical to the photoluminescent silicone rubber as alaser target, by the Fourier-transform infrared spectroscopy. The deposited thin films emitted white light under anillumination of 325 nm He-Cd laser as same as the case of the photoluminescent silicone rubber target. Also, thephotoluminescence spectra of the deposited thin films could be controllably changed by varying the single pulse laser
fluence. In addition, the thin films of the photoluminescent silicone rubber area-selectively deposited in micron sizegave emission of white light under the illumination of He-Cd laser as well.
Keywords: Photoluminescence, Silicone rubber, Pulsed laser deposition, ArF excimer laser, Area-selective deposition

1.

Introduction

photoluminescent silicone rubber was ablated in a vacuum

Silicone ([SiO(CH3)2]n) rubber is chemically stable and haschamber by the intense ArF excimer laser, and thin films of thesuperior properties such as a heat-, cold- or chemicals-resistance,

photoluminescent silicone rubber were deposited on a substrate.

in addition to the high optical transparency in UV to IR region.

In the present work, based on the compositional fidelity of PLD,

Thus, the silicone rubber is widely used for scientific andthin films of the photoluminescent silicone rubber was deposited

industrial uses; it is currently used for an optical waveguide,on other material except silicone rubber. The PL emitted from thesealing material and lens material of UV- and white-LEDs, fordeposited thin films under the illumination of He-Cd laser wasinstance [1]. Recently, we have reported on the photochemicalmeasured when the single pulse laser fluence was varied.

modification of silicone rubber using a 193 nm ArF excimer
laser; the silicone rubber modified by a faint beam of the ArF

2.

Experimental method

excimer laser gave emission of white light under an illumination

A laser beam generated by an ArF excimer laser (Lambdaof 325 nm He-Cd laser [2,3]. The chemical bonding of thePhysik, EMG202MSC) irradiated the surface of 2-mm-thickmodified silicone rubber was found to be a silica-like silicone,silicone rubbers (Togawa Rubber, K-125) in air without a lens.

and the photoluminescence (PL) derived its origin from oxygen

The single pulse fluence of ArF excimer laser on the silicone

deficiency centers and peroxy-centers of silica structure in therubber surface was 40 mJ/cm2. The pulse duration wasmodified silicone rubber [4-6].

approximately 23 ns, and the repetition rate was 10 Hz. The

In this paper, we expanded the previous our work on thephotochemical

modificationofsilicone*Corresponding author: (電子メールアドレス)

rubber;theirradiation time was 20 min. For subsequent PLD, the modified
silicone rubber was immersed in 1 wt.% HF water solution for 30

min to etch the 15-µm-thick surface of the modified layer

fluence, velocity of ejected species from the target becomes high;including a 0.5 mm-thick SiO2 top layer, as show in Fig. 1,

the ejected species can be easy to react with residual oxygen

because the intense PL was actually emitted at a depth of 15 tomolecules in the chamber.

50 µm in the modified silicone rubber.

∫ H・dl = I

(1)

C

3.

Results and Discussion

Under the illumination of a 325 nm He-Cd laser, the change of

3.1 Thin film deposition

the PL color was clearly observed. The multimode He-Cd laser

Figure 1 shows the single pulse laser fluence dependence ofirradiated the surface of the films deposited at the single pulse

the thickness of the deposited films. The laser fluence on thelaser fluences of 7.5, 10 and 20 J/cm2. The PL color could betarget surface was varied from 5 to 7.5, 10 and 20 J/cm2. The

controllably changed from bluish white to yellow by varying theirradiation time was 20 min. The thickness of the deposited films

single pulse laser fluence. The PL spectra of the deposited films

was measured to be 0.2, 1.2, 3.8 and 3.8 µm, respectively. The

were stable in air for a half year at least.

deposited films was yellowish white in color and was adhered
Table 1 Current as a function of voltage

closely to silica glass substrate460
in oxygen

Peak wavelength (nm)450

Voltage [V]12345678Current [A]2468

10121416

in air

440
4.

430

Conclusions
The photoluminescent silicone rubber was ablated by the 193

420

nm ArF excimer laser to deposit the thin films of the410

photoluminescent silicone rubber on the silica glass substrates.
The chemical bonding of the deposited thin films was almost

400

identical to the photoluminescent silicone rubber target, under
the compositional fidelity of the PLD. The deposited thin films

3900102030405060

Irradiation time (min)emitted white light under the illumination of 325 nm He-Cd laser.
The PL spectra of the deposited thin films could be controllablychanged by varying the single pulse laser fluence. In addition,

Fig. 1 Irradiation time dependence of the peak wavelength of
PL spectra of the silicone rubber modified by the ArF
excimer laser in oxygen gas and in air.

the thin films of the photoluminescent silicone rubberarea-selectively deposited in micron size also gave emission
under the illumination of 325 nm He-Cd laser. This result will

3.2 PL spectra
Table 1 shows the PL spectra of the deposited films at threeopen up the fabrication of the silicone rubber-based, light andflexible display, lighting or microchip for photonic application.

different single pulse laser fluences. All the deposited films were
kept at approximately 1 µm in thickness by adjusting the laser
irradiation time and were confirmed to be photoluminescent,though the PL intensity was weak compared to the target due toAcknowledgements
The authors are grateful to Ms. Minako Iyono, National
Defense Academy, for assistance in experiments.

the thin thickness of the deposited films. At the laser fluence of
7.5 J/cm2, the PL spectrum was almost same to the target. With
increasing the laser fluence, the PL spectrum was shifted toward
red. Thus, the PL spectrum could be controllably changed byvarying the single pulse laser fluence. By increasing the laser

References[1] D.B. Chrisey and G.K. Hubler, Pulsed Laser Deposition.
Willy, New York, 55 (1994)[2] M. Okoshi, D. Sekine, N. Inoue and T. Yamashita, Jpn. J.
Appl. Phys. 46, 356 (2007)