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36 PCB007 MAGAZINE I DECEMBER 2021 We know that if you walk on the porch, you can get injured, so we prevented access. e full corrective action would be for the man to heal, get a job and repair the porch. Once complete, the restrictions to the porch can be removed and life will continue as normal. Right? Wrong. We are forgetting something— preventive maintenance. We need to add a step, so the man inspects the porch on a rou- tine basis to identify any problems in an early stage to prevent recurrence of the initial prob- lem. Now we have officially closed the loop. You see, we tend to accept things prema- turely as we get older. We make assumptions based on life experiences. is can be problem- atic in process development and maintenance. We need to question more when necessary. Any nonconformance, whether it be on the man- ufacturing floor, electrical test, or in our daily routines can utilize the Five Whys discipline. Most, if not all nonconformance issues, can be rooted down five levels at least. Don't give up too early. To find true root causes, it takes some critical thinking. Just because a brainiac created the process or activity doesn't mean they cannot be wrong. Even the smartest of minds are wrong some of the time. We all are. Ask questions. Happy holidays to all my readers. It is with your support that I keep writing. My best to all of you and your families wherever you may be. PCB007 Todd Kolmodin is VP of quality for Gardien Services USA and an expert in electrical test and reliability issues. To read past columns or contact Kolmodin, click here. Princeton researchers have created the world's purest sample of gallium arsenide, a semiconduc- tor used in devices that power such technologies as cell phones and satellites. The team baked their material down to one impu- rity for every 10 billion atoms, reaching a level of quality that outstrips even the world's purest silicon sample used in verifying the one-kilogram standard. The finished gallium arsenide chip, a square about the width of a pencil eraser, allowed the team to probe deep into the very nature of electrons. Rather than sending this chip to space, the researchers took their ultra-pure sample to the base- ment of Princeton's engineering quadrangle where they wired it up, froze it to colder-than-space tem- peratures, enveloped it in a powerful magnetic field and applied a voltage, sending electrons through the two-dimensional plane sand- wiched between the material's crys- talline layers. As they lowered the magnetic field, they found a surpris- ing series of effects. The results showed that many of the phenomena driving today's most advanced physics can be observed under far weaker mag- netic fields than previously thought. Lower magnetic fields could empower more labs to study the mys- terious physics problems buried within such two- dimensional systems. More exciting, according to the researchers: These less severe conditions pres- ent physics that have no established theoretical framework, paving the way for further exploration of quantum phenomena. One surprise came when the electrons aligned into a lattice structure known as a Wigner crys- tal. Scientists previously thought Wigner crystals required extremely intense magnetic fields, around 14 Tesla. "Strong enough to levitate a frog," said Kevin Villegas Rosales, one of the study's two first authors, who recently completed his Ph.D. in elec- trical and computer engineering. But this study showed that electrons can crystallize at less than one Tesla. "We just needed the ultra-high qual- ity to see them," he said. (Source: Princeton University) Ultra-pure Semiconductor Opens New Frontier in Study of Electrons

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