Feature: Thermal management
Solutions to many of these challenges can be found by considering advanced novel materials, such as energy-efficient semiconductors, organic photovoltaics, 2D coatings for sensitive components, and ultra-thin semiconductors and insulators. Unlocking the benefits of these materials requires a deep
understanding of their properties, particularly how their performance or stability varies under the environmental conditions found in real-world applications. Such sample characterisation can be done using well-established techniques like Raman, FT-IR and X-ray spectroscopy, using instrument stages that allow experiments to be carried out under a range of conditions of temperature, atmosphere and vacuum pressure. Here we will discuss two applications where being able to
precisely control the temperature of the material has made a significant contribution to understanding its properties.
Novel materials for microelectronics offer better temperature control
By Duncan Stacey, Sales and Marketing Director, Linkam Scientific Instruments
N
ew materials with exciting properties are constantly being proposed for microelectronics applications, but there is a challenge: a lack of understanding about how they perform under real-world environmental conditions. As the demand for microelectronics continues
to increase, electronic design and development engineers face numerous challenges, such as reducing energy consumption, increasing battery storage capacity whilst shortening battery charging times, and incorporating sustainable materials – yet at the same time reducing the size and weight of components.
Studying crystallographic phase transitions X-ray diffraction (XRD) generates diffraction patterns that correlate directly with the presence of certain components in a material, giving a picture of the phases present and defect details. XRD was historically used to examine crystalline materials, but
two refinements of the technique are now used to study non- crystalline and semi-crystalline materials in powder and liquid form. Wide-angle X ray scattering (WAXS) measures scattering at 2θ angles of >5°, and provides structural information down to 0.1nm, similar to traditional XRD. Small-angle X ray scattering (SAXS) measures scattering at 2θ
angles of 0-5°, and provides information on complex molecules and materials such as polymers, colloids and porous materials, with a feature size of up to 500nm. The Centre for Nature-Inspired Engineering (CNIE) at the
Department of Chemical Engineering of University College London has a SAXS/WAXS system. It is fitted with several stages to vary the conditions under observation, including a temperature-controlled stage for experiments between -175°C and 350°C, and a capillary X-ray stage for observing small volumes of materials at temperatures from 4°C to 80°C. Te set-up at CNIE has been used to detect new polymorphs
and phase changes in both solid and liquid samples. A good example of this is the analysis of two phase transitions in pyroglutamic acid (PGA); see Figure 1. It was found that the low-temperature phase change, from the α' to the α phase, happens slowly and appears to be martensitic (a hard and very brittle solid solution), in which the strain at the α–α' interface in partially-transformed crystals caused the transformation to occur in bursts. Applied to the microelectronics field, this opens up the prospect of detecting new polymorphs and phase changes in novel materials that might have consequences for real-world applications.
The protective effect of 2D coatings for copper Electronic components must be protected as much as possible from environmental stresses, and materials that are a single- atom-layer thick, i.e., 2D materials, are now receiving attention
www.electronicsworld.co.uk November 2022 33
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