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Since biblical times, Mediterranean people have cultivated the carob tree. Its seeds, called carats, are remarkably consistent in mass, about 200 milligrams each. For ages, the carat weight has been a measure of gemstones and other valuable items. The Roman pure gold solidus coin weighed 24 carats; it was the original 24-carat gold. Mobile device displays may soon be described in carats along with pixels and inches. This is because Apple is getting into the sapphire sheet business.
It might make a monkey of Corning's Gorilla Glass, because wherever Apple leads, the rest of the technology world usually follows.
Sapphire has a number of uses in high technology devices. For instance, some semiconductors are built on a sapphire rather than silicon substrate. But the future of sapphire for Apple is expected to be a different use of the material. Sapphire can be used for the face of scratch-resistant displays, much the way it is currently used to make top quality watch crystals and other optical parts. All these applications are based on the key physical characteristics of sapphire: its hardness, its ability to provide electrical insulation and its ability to carry heat, even as it blocks the flow of electricity.
While sapphire as a gemstone is usually blue, in optical applications it is clear. The difference stems from impurities in the crystalline aluminum oxide that we call sapphire. The same type of crystal with different impurities can be red rather than blue, and when we find this crystal in nature we call it a ruby. The name of the family of minerals made of this material is corundum, and it includes yellowish and orange stones as well as red and blue ones.
Whether sapphire or ruby, natural or manmade, aluminum oxide crystals are very hard. They are rated 9 on the Mohs hardness scale. Diamond, rated 10, is harder, but Corning's family of Gorilla Glass products, is not. Gorilla Glass display faces have has some physical and economic characteristics that give them an advantage over sapphire . . . for now. But that could change. While it is likely that sapphire will always be more costly than Gorilla Glass, it is just as likely that in some applications the superior hardness of sapphire will make it a winner, much the way sapphire watch crystals are so often used in fine timepieces.
Additionally, sapphire display surfaces seem particularly suitable for Apple products for a number of reasons. Apple devices have long technical and economic lives, not only with their initial owners but also in the aftermarket. (So do Kindle ebooks and tablets, but I can't think of any other client devices with comparable persistence.) Consumers seem to trust Apple to make products that don't require pampering. While many people get cases, bumpers, or neoprene pockets for their iThings, many do not; iPhones are often carried in pockets or purses alongside keys, and iPads are often just tossed into cluttered backpacks. Those are some practical reasons for Apple to enhance its products with superior display faces. But that isn't all to this matter. Apple's customers really love their gadgets. A sapphire face would boost the allure of an iPhone, iPad or, if one were to emerge, an iWatch.
Sometimes it seems as if Apple products are held in such reverence that the most enthused Apple fans constitute some kind of cult. At the extreme, users' lives seem to revolve around their iPhones and, to a lesser extent, their iPads and iPods. If Apple were a religion rather than a maker of high-tech products, its vaunted devices would be candidates for canonization. And the most fervent fanbois might adorn their gadgets with sapphires and other jewels, the way passionate admirers of saints have embellished and bejeweled relic skulls and bones.
Apple relics have already been established as objects of considerable value. An Apple I, forerunner of the Apple II computer that first put Apple on the map, was sold for nearly $400,000 at auction last summer. Somewhere in medicine's physical archives are relics of Steve Jobs, whose medical history included a number of biopsies, some or all of them very likely preserved for scientific posterity. If a religion ever pops up in which Jobs is a saint or something more, those relics or items purporting to be Jobs' relics could end up in Jobsian cathedrals.
There must be a dozen purported heads of St. John the Baptist in North Africa, the Middle East, Europe, and possibly elsewhere. The Pope seems to believe the real thing is in Rome, in an ancient church near the big post office. John is venerated as the saint who baptized Christ. John's wanderings in the desert may well have involved a diet of carob, which is why the plant's pods are sometimes called St. John's Bread. It turns out that carob and St. John are woven together in many ways and in many places. On the island of Malta, where carob not only grows well but served as a vital foodstuff during World War II, for instance. A thousand years ago on Malta, knights of the Hospitallers collected relics they sincerely believed were the bones of St. John.
As entertaining as some of the stories surrounding relics of St. John might be, few are as exotic as the real scientific story behind the sapphire-cutting technology that has captivated Apple's attention and a pile of its money, too. In order to get a lock on very thin sheets of sapphire, Apple is putting more than a half billion dollars into a factory that will peel very thin layers of sapphire off a chunk of the material. The chunk is called a boule. The company doing the sapphire splitting is called GT Technology and its process, originally developed for use in conjunction with the fabrication of solar panels on a sapphire substrate, is close to magic.
In 2012, an outfit called Twin Creeks found a way to beam hydrogen ions at a sapphire boule in a way that made them build up in a layer about 20 micrometers below the surface of the sapphire. Once this had been done, the ions could, with the addition or some electrons, be turned into hydrogen atoms. At that point the layer, which had fit within the sapphire crystal lattice very nicely, became real hydrogen gas and its presence caused the crystal to split. The thin layer above the hydrogen, a 20-micrometer layer, could be harvested. The process could be repeated, with each cycle yielding a very thin sheet of sapphire. Twin Creeks was acquired by GT Technology, and GT cut the deal with Apple that will give GT a very nice factory for making sapphire sheets and give Apple access, presumably exclusive access, to the sheets made at that factory.
So now Apple is just a few steps and several months away from making (or getting a supplier to make) device screens that have as their external surface an ultra-thin, incredibly hard, optically clear, electrically insulating layer of sapphire. The sapphire will most likely be bonded to some kind of glass to form a complete screen that provides both display and touch-sensing features.
Notwithstanding all the positive reports in the press, this whole venture could turn out to be a bust. Maybe the process won't work as expected. Maybe the costs will be so high that the sapphire display screen will remain impractical, even for Apple, which can command premium prices for its products. But even so, such an unfortunate development wouldn't stop Apple from moving forward. It has plenty of cash on hand. It could cut this kind of deal ten times, if that's what it took to obtain a key technological advantage, and still have more than enough money in the bank to fight off the insipid Icahnbirds it attracts.
Steve Jobs is gone, but Apple's current management seems to be plenty smart and its corporate culture is lively and as creative as ever. Apple is quite capable of taking a long view. It has that kind of vision. And these days it is looking at the future through a sapphire lens others are only beginning to fully appreciate.
— Hesh Wiener December 2013