Nano-oxide thin films deposited via atomic layer deposition on microchannel plates

Abstract

Microchannel plate (MCP) as a key part is a kind of electron multiplied device applied in many scientific fields. Oxide thin films such as zinc oxide doped with aluminum oxide (ZnO:Al2O3) as conductive layer and pure aluminum oxide (Al2O3) as secondary electron emission (SEE) layer were prepared in the pores of MCP via atomic layer deposition (ALD) which is a method that can precisely control thin film thickness on a substrate with a high aspect ratio structure. In this paper, nano-oxide thin films ZnO:Al2O3 and Al2O3 were prepared onto varied kinds of substrates by ALD technique, and the morphology, element distribution, structure, and surface chemical states of samples were systematically investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoemission spectroscopy (XPS), respectively. Finally, electrical properties of an MCP device as a function of nano-oxide thin film thickness were firstly studied, and the electrical measurement results showed that the average gain of MCP was greater than 2,000 at DC 800 V with nano-oxide thin film thickness approximately 122 nm. During electrical measurement, current jitter was observed, and possible reasons were preliminarily proposed to explain the observed experimental phenomenon.

The Design of the AZO Conductive Layer on Microchannel Plate

“…The material is deposited on the substrate in the form of a monoatomic film surface. ALD can produce a continuous film without pinholes, with excellent coverage, and can control the thickness and composition of the atomic film [ 1 , 2 , 4 , 11 , 13 , 19 , 20 ].…”

“…In this condition, we define the corresponding MCP resistance as the non-working resistance of the MCP. We use a Keithley model 6517B electrometer to measure the non-working resistance of the MCP in a 10 −3 –10 −5 Pa vacuum [ 1 , 4 , 13 ].

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“…The electron gun provides incident electrons to the MCP, and the phosphor screen receives the electrons output by the MCP. In addition, when the MCP is under operation, the high-voltage phosphor screen will emit green light to detect the uniformity of the MCP [ 1 , 21 ].…”

“…Microchannel plate (MCP) is an electron multiplier composed of two-dimensional pore arrays by thin glass plate form integration, length of 0.5–5 mm, a 4–40 μm diameter and with a bias angle usually 5°–13° to the normal of the plate surface; the open area ratio of the plate is up to 60%, and the high length-to-diameter ratio in each pore is about 20:1 to 100:1 [ 1 ].…”

“…MCP can integrate into various kinds of instruments, including photoelectric detector, photomultiplier tubes (PMTs), ultraviolet spectrometer, cathode ray tube, scanning electron microscope, field emission displays, residual gas analyzer, medical imaging, time-of-flight mass spectrometry, night-vision goggles, etc. [ 1 , 4 , 7 – 9 ]. The hydrogen firing of the traditional process makes the microchannel suitable conductivity and secondary electron emission coefficient.…”