Generation of organic ion beams having an amino functional group

Radial. Phys. Chem. Vol. 43, No. 3, pp. 303-305, 1994 Printed in Great Britain. All rights reserved

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0969-806X/94 $6.00 ÷ 0.00 Pergamon Press Ltd

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LETTER TO THE EDITORS

GENERATION OF ORGANIC ION BEAMS HAVING AN AMINO FUNCTIONAL GROUP Takasaki

MASAO TAMADA, YOSHINOBU Izuasi and HIDEK1 Oancm Research Establishment, Japan Atomic Energy Watanuki 1233, Takasaki, Gunma 370-12, Japan

Radiation Chemistry

Research

Institute,

(Received 28 August 1992; accepted 5 October 1992) Abstract—Beams of organic ion which have an amino functional group like ~CH

2NH2 were generated 2 at 30gas keY.with an organic ion beam accelerator. The current density by using n-propylamine as an ion source of ~CH2NH2 beam was 7.5 nA/cm Ion beam irradiation has been applied to the modification in the outermost region of polymers in order to, for example, produce conductive polyimides (Marletta, 1990; Davenas et a!., 1988; Fink et a!., 1988; Yoshida and Iwaki, 1987; MarIetta eta!., 1989), p—n junction of polyacetylene (Wada et a!., 1987), silicon rubber for medical usage with enriched wettability (Suzuki and Kusakabe, 1988) and poly(lhexane) with compatibility between tissue and blood (Carlson et a!., 1985). These modifications are controlled by changing metallic ions with different bornbardment density and ion energy. The obtained function through these modifications, however, was restricted by the combination of polymers and irradiated ions. If such organic ion beams like + CH 2NH2 could be generated, the modification of polymers would be much progressed. The present paper deals with a new attempt of generating organic ion beams. Figure 1 shows a scheme of the organic ion beam accelerator. A source gas is introduced into a RF

ion source with 100 MHz and 200W. As source gases n -propylamine (M~= 59) and n-butane (M~= 58) were used. The pressure of the introduced gas in the RF ion source was adjusted to 5 x i0~Pa by a needle valve. The maximum powers of solenoid coil and probe are 50 V, 6 A and 8 kV, 30 mA, respectively. In the RF ion source the gas is converted to plasma composed of many kinds of fragmentary ions. These fragmentary ions are extracted from the RF ion source by exerting a voltage of 10 kV. Then, the fragmentary ion beam is roughly focused by the Einzel lens. The ion beam of selected M/e at a certain magnetic field is introduced to the variable slit for a further separation. The maximum magnetic flux density is 0.6 T which can separate the fragmentary ions up to M/e 120. After going through the slit, a fragmentary ion is further accelerated to 30 keV. Finally, the organic ion beam of selected M/e reaches a position for a substrate. Elnzel lens Magnet

Soume gas

RF Ion souice Variable slit Mcelerate tube

Substrate

Fig. I. A scheme of an organic ion beam accelerator. 303

Letter to the

304

To investigate the extraction of an organic ion beam by changing the width of variable slit, beam currents were measured at various magnetic fields. The power of RF ion source, current for solenoid coil, voltage for probe, and voltage for extraction

~

electrode 10 kV, respectively. were The to fragmentary 46W, 3.6 A, ionthe 0.6 beam kV was and accelerated upbeam toadjusted 30currents keV. Figure 2 shows relationship between obtained from n -propylamine at substrate position and M/e at slit widths of (a) 8mm, (b) 1 mm and (c) 0.1 mm. At the slit width

I 2$

__________________________________ Mb Fig. 2. Relationship between beam currents at the substrate position and M/e at various slit widths: (a) 8 mm, (b) 1 mm and (c) 0.1 ~

Table 1. Peak currents offragmentary ions of n.propylamine and n-butane at various Mfe values obtained at the variable slit width of0.1mm and their ratios Peak current5 (arb. units)

__________________________ n-Propylamine (Ce) 0.47 0.45 2.30 3.31 0.47

n-Butane (C5) 1.40 1.38 0.16 0.23 0.31

25 26 27 28 29 30

0.32 1.42 1.23 3.67 1.00 3.04

0.14 2.56 0.98 1.33 1.00 0.10

2.3 0.55 1.3 2.8 1.0 30

39 40 41 42 43 44

0.27 0.18 0.34 0.39 0.23 0.11

0.39 0.27 0.58 0.40 1.18 0.08

0.69 0.67 0.59 0.98 0.19 1.4

M/e 14 15 16 17 18

Editors

C~/C5 0.34 0.33 14 14 1.5

56 0.11 0.09 1.2 57 0.15 0.18 0.83 58 0.38 0.01 38 59 0.11 normalized by —the height at — 5Peak currents were M/e 29 corresponding to a common fragmentary ion ~CH 2CH, ohtamed from both n-propylamine and n-butane.

of 8 mm, the M/e region between 10 and 20 corresponding to the fragmentary ions containing one carbon atom or one nitrogen atom, were separated to several peaks. The separation was slightly improved with decreasing width to 1 mm as shown in Fig. 2(b). The peak currents in the vicinity of M/e 28 were 18 and 3.5 p A/cm2 for slit width of 8 and 1 mm, respectively. Especially in Fig. 2(c) the decrease of slit width to 0.1 mm was effective on the separation of fragmentary ions in the region between 20 and 43. In this case, 4 large peaks appeared at M/e 28, 17, 30 and 16 in the decreasing order. The peak currents of each peak are 9.1, 8.2, 7.5 and 5.7 nA/cm2. As a result, the accelerator was capable of introducing an organic ion beam of selected M/e to the substrate position. To identify the peaks of beam currents, the peak heights at several M/e values of n -propylamine were compared with those of n-butane as shown in Table 1. It is expected that the peak heights originated from amino groups of n -propylamine should be larger than those for n-butane. As shown in Table 1, the peak height ratio Cp/CB at M/e of 16, 17, 30 and 58 are obviously large. By considering that the mass spectrum of n-propylamine (MacLafferty and Stauffer, 1989) has a maximum peak at M/e = 30 corresponding

+

CH

2NH2, we assigned these peaks to ~NH2(M/e = 16), ~NH3(17), ~CH2NH2(30)and + CH2CH2CH2NH2(58), respectively. The ratio at M/e 28 is not so large though the peak showed the highest beam current in Fig. 2(c). This is probably due to the fact that this peak corresponds to mixture of + CH=NH originated from n -propylamine and ~[CH2=CH2]from both n-propylamine and n-butane. By using this organic ion beam accelerator, we can generate various ion beams containing an amino functional group with maximum energy of 30 keY. It will be possible to introduce these organic ion beam onto polymeric substrate in order to modify its surface. REFERENCES Carison J. D., Bares J. E., Guzman A. M. and Pronko P. P. (1985) Surface property changes induced in poly(lhexene) elastomer by high energy ion irradiation. Nuci. lnstrwn. Met/i. B7/8, 507. Davenas J., Boiteux 0., Xu X.byL.ion andbeam Adem E. (1988)inRole of the modification induced irradiation the optical and conducting properties of polyimide. Nucl. Instru,n. Met/i. B32, 136.

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