Coating and functionalization of high density ion track structures by atomic layer deposition

Laura Mättö,Imre M Szilágyi,Mikko Laitinen,Mikko Ritala,Markku Leskelä,Timo Sajavaara

doi:10.1016/j.nima.2016.06.132

Abstract

In this study flexible TiO2 coated porous Kapton membranes are presented having electron multiplication properties. 800nm crossing pores were fabricated into 50 μm thick Kapton membranes using ion track technology and chemical etching. Consecutively, 50nm TiO2 films were deposited into the pores of the Kapton membranes by atomic layer deposition using Ti(iOPr)4 and water as precursors at 250°C. The TiO2 films and coated membranes were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray reflectometry (XRR). Au metal electrode fabrication onto both sides of the coated foils was achieved by electron beam evaporation. The electron multipliers were obtained by joining two coated membranes separated by a conductive spacer. The results show that electron multiplication can be achieved using ALD-coated flexible ion track polymer foils.

Highlights

Porous materials with precisely controlled properties, such as pore size and diameter, have several applications in, for instance, filtration [1], gas sensing [2,3], catalysis [4], photocatalysis [5,6], solar cells [7], adsorption [8,9], and biomedical research [10]
The deposition of the Atomic layer deposition (ALD) TiO2 film was successful on polyimide even at a growth temperature of 250 oC (Fig. 3)
If the voltage difference over the ALD-Kapton stack is negative, there is no voltage dependence as the possible electrons are accelerated away from the Microchannel plates (MCPs) and the count rate of about 12 counts per second is comparable to the background count rate of the MCP, with or without any backscattered oxygen ions

Summary

Introduction

Porous materials with precisely controlled properties, such as pore size and diameter, have several applications in, for instance, filtration [1], gas sensing [2,3], catalysis [4], photocatalysis [5,6], solar cells [7], adsorption [8,9], and biomedical research [10]. ALD can be used to coat flat substrates, and complex surfaces and highly porous materials with uniform films having thickness even down to single nanometers [15,16]. These films can be, for instance, insulating oxides or conducting metals, ternary compounds or polymers [17,18]. In this study ALD was used to grow TiO2 films on the sub-micron diameter ion track structures in order to have low-resistivity and enhanced secondary electron production in the pores. The substrate for ALD in our case was a highly flexible porous ion track polyimide (Kapton) (Fig. 1)

Experimental

Results and discussion

Conclusions