Henrik Sønsteby, below, holds a silicon wafer covered with a thin film – the colours caused by unintentional thickness variations – consisting of oxygen, niobium and potassium/sodium, which are shown in the inset as red, brown and purple respectively
for electronics?
LEAD: THERE IS NO SAFE LOWER LIMIT
products, which for a large part end up as waste electrical and electronic equipment (WEEE) when new and cooler gadgets become available. This means that the amount ofWEEE is constantly increasing worldwide. “The problems with lead pollution aremuch
greater in China and the other countries that produce the electronic products we have become completely dependent on, but that doesn’tmean that we shouldn’t care in Europe,” says Sønsteby. Lead is often used inmaterials that are
piezoelectric, crystals that produce an electrical voltage when pressure is applied. Thesematerials are widely used as pressure sensors. Themost extensive use of piezoelectric and lead-
basedmaterial occurs in transmitters and receivers, where the ceramic compound lead zirconate titanate (PZT) has been difficult to replace. PZT contains approximately 60 per cent lead by weight. The thin filmthat Sønsteby and colleagues have produced
now offers a realistic alternative. The innovative thin filmconsists of crystals, which
Sønsteby creates by depositing one atomic layer at a time on a substratemade of silicon. “In principle, I believe that we have opened a new door bymaking it possible to produce new types ofmaterials using ALD. Cheaper battery technology, superconductors and thermoelectricmaterials can benefit fromthis,” says Sønsteby. He adds that there are still some issues that need
to be solved before the new thin films can be used in products. “Now we are able to produce the films in the
laboratory, the next step is to find a way to produce quantities that are large and cheap enough to be used industrially,” he says. “Wemust also find a way to produce crystals
where all the piezoelectric properties point in the same direction, before thematerials can be used as sensors or smallmotors.” EE
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August 2017 /// Environmental Engineering /// 47
According to the World Health Organization (WHO), there is no limit below which lead in the bloodstream can be seen as not harmful. Exposure to lead is linked to reduced intelligence, learning difficulties, and behavioural problems, such as reduced impulse control and attention. The correlation between lead exposure and reduced intelligence is very strong and is today considered the most critical effect of lead. Lead in the blood of pregnant women crosses over to the foetus, so that exposure can start even before birth. Children, pregnant women and women of childbearing age constitute particularly vulnerable groups to lead exposure, and even low exposure may cause harmful
effects. Source: The Norwegian Environment Agency
PICTURE: BJARNE ROESJOE/UIO
ILLUSTRATION: HENRIK SØNSTEBY/UIO
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