Recent Results

We have now demonstrated that Platypus can deal with films out to 325 nm with sufficient resolution to get a very accurate determination of the total thickness.
 

Figure 1: Atomic Layer Deposition

The image above shows Atomic Layer Deposition (ALD) Al₂O₃ film on Si. Thanks to Gerry Triani for preparing this special alumina film for us. Data are collected in high-resolution setting; fitted to 3246(2) Å. The green curve shows X-ray reflectivity data (poor contrast between Al₂O₃ and Si).
 

Fgiure 2: Specular Reflection

In July 2008, Platypus took its first data from the OPAL reactor. Early weeks were focused on developing instrument control and data-acquisition systems and collecting the first time-of-flight neutron spectra for the cold guide 3 (Platypus’ location) shown in the figure below.

Figure 3: The Platypus cold neutron spectrum

At the heart of Platypus is the Astrium disc-chopper system which allows the wavelength resolution of neutron pulses to be tailored to suit the system under study. By decreasing the Dl/l resolution from 1.3% to either 4.5% or 10%, the neutron flux increases 3 times and 7 times, respectively. The figure shows the Platypus neutron spectrum for different disc-pair combinations.

Figure 4: Measuring the reflectivity of solid films

To date we have measured the reflectivity of several thin solid-films (polymers, metallic multilayers and gold). Below you see very early reflectivity data from a 340 Å spin-coated polystyrene film on Si.

Figure 5: Reflectivity data collected from alumina film

Detector image of reflectivity data collected from a ~1450 Å alumina film on Si (produced by Atomic Layer Deposition - ALD) are displayed in the figure below.

Figure 3: Thick Films

Observed and fitted reflectivity data from this film are shown in the next figure (Dl/l~1.3%), demonstrating that Platypus is capable of measuring relatively thick films: d = 1452 Å; scattering-length density (SLD) = 4.43x10^-6 Å^-2; s = 5.3 Å.

Figure 7: Data from a Bragg Mirror of 25 bilayers

Data from a Ni/Ti multilayer “Bragg Mirror” of 25 bilayers (Ni: 113.4 Å / Ti: 79.9 Å) were collected at (Dl/l~1.3%), see below.

Figure 8: First measurements on a free-liquid surface

First measurements on a free-liquid surface of D₂O were also successful, but there are plenty of tuning and commissioning tasks ahead of us. Systems to conduct polarised neutron reflectometry experiments are currently being manufactured, and will be installed and commissioned in 2009.

The application for an operating licence is expected to be submitted in October.