Sapphire beyond the smart watch

Some day in the not-so distant future, our way of interacting with the world around us will be vastly different. Technology that seems like science fiction today – such as glasses with heads-up displays and connected headbands – will be the norm for average people. Desktop computers will be technologically archaic and non-smartphones will simply no longer exist.

3D Display

But before we get too carried away, let’s rewind to the present.

The Apple Watch broke ground for the consumer wearable device segment this year after it was reported last week that over 4.2 million units have been shipped since April 2015. According to research firm Canalys, Apple has easily overtaken more established companies like Fitbit and Xiaomi in just three months.

But while the smartwatch market gradually gains momentum, the augmented reality and wearables industries overall still face many obstacles on the road to success, especially in the form of consumer devices.

Photonics Spectra recently noted three challenges these industries must overcome before wearables can achieve wider consumer interest and, ultimately, adoption.

1)      System cost

2)      Materials

3)      Practical use

With the development of a wearable device, comes the need for a screen material that can put up with the rigors posed by exposure to the environment. Specifically, these devices are generally in more vulnerable locations than a phone. Fortunately, sapphire is a solution that is becoming more obtainable due to new manufacturing techniques.

Although currently more expensive than glass, sapphire’s greater scratch resistance, strength and durability allows products to be thinner, which can be a plus in wearables considering consumers desire their devices to blend in as stylish fashion accessories.

In addition, sapphire manufacturers are continuing to innovate by developing new solutions for the next generation of wearables. One such solution, sapphire coated glass, will give companies the ability to develop screen covers that are not only strong, but can mold to curved devices. These coatings will be directly applied on top of glass and will provide similar durability as sapphire, at a lower cost.

Already prominently used on a variety of mobile and wearable devices, including the Apple Watch, sapphire will likely be used on the screens of many cutting edge gadgets. As production methods continue to improve, the futuristic applications for sapphire are limitless.

Sapphire – Quality Matters, Part 2: Transmission Quality

Recently, Novus Light Today published an article by Dr. Jonathan Levine, Director of Technical Business Development at Rubicon Technology, about sapphire quality.  His article shares a thorough review of the measures of sapphire quality for optical-grade applications.  Last week, we looked at the first two metrics, chemical analysis and X-ray rocking curves.  This week, we’ll look at transmission quality.

Levine writes that the quality of a sapphire is determined by how closely the grown crystal matches the ideal structure with respect to the arrangement of atoms within the lattice, dislocations, defects, and stress.  Root causes for these problems often originate from insufficient purity of the starting material and the growth process itself.

Sapphire exhibits excellent transmission in the ultraviolet (UV) to the mid-infrared (IR) range (~200 – 5000 nm).   According to Levine, conditions within the sapphire growth furnace can induce subtle interactions between the molten sapphire and the growth environment.  These interactions can produce bubbles, dislocations and other stresses that could impact optical performance.   Levine says that carefully controlling the growth environment produces sapphire that maintains excellent transmission at 200 nm through the mid-IR wavelengths.  He illustrates the impact of furnace interactions by comparing Rubicon’s ES-2 sapphire with another commercial sapphire maker’s crystal produced using a different growth method in the figure below.  From the image in the post, you can see a sharp absorption peak at 200 nm for sapphire produced by the commercial maker that is absent in sapphire grown by Rubicon.

Optical transmission of sapphire depicting a sharp absorption peak at 200 nm for sapphire produced by a commercial producer that is absent in sapphire grown by Rubicon.  Inset: Optical transmission for Rubicon sapphire from the visible to mid-IR range approaching 90% due to the high quality of the material.

Optical transmission of sapphire depicting a sharp absorption peak at 200 nm for sapphire produced by a commercial producer that is absent in sapphire grown by Rubicon. Inset: Optical transmission for Rubicon sapphire from the visible to mid-IR range approaching 90% due to the high quality of the material.

For Further Reading

Novus Light Today, Optical-Grade Sapphire, Where Quality Matters, http://www.novuslight.com/optical-grade-sapphire-where-quality-matters_N1596.html#sthash.giGipxT1.dpuf

Sapphire Quality Matters: Part 1

Sapphire is an extremely versatile material with a growing list of applications in a wide range of industries.  Sapphire suits optical applications because of its scratch resistance and its transmission characteristics.  You’ll find sapphire components such as lenses and windows in medical equipment, lasers, satellites, aircraft, flame detectors, smart phones, cameras and watches.  Recent advances in sapphire crystal growth technology and fabrication have improved the performance, purity, and availability of sapphire for all types of applications.

Recently, Novus Light Today published an article by Dr. Jonathan Levine, Director of Technical Business Development at Rubicon Technology, about sapphire quality.  His article gives a thorough review of the measures of sapphire quality for optical applications.  Levine writes that the quality of a sapphire is determined by how closely the grown crystal matches the ideal structure with respect to the arrangement of atoms within the lattice, dislocations, defects, and stress.  Root causes for these problems often originate from insufficient purity of the starting material and the growth process itself.

The effects of these variables in the final product are commonly quantified by three metrics: chemical analysis, X-ray rocking curves, and optical transmission.  Additionally, the observance of bubbles in the crystal provides a baseline from which crystal quality is determined because bubbles serve as scattering centers for any light transmitted through a sapphire optic, thus reducing its performance.

This week, we look at the first two metrics, chemical analysis and X-ray rocking curves.

Powdered aluminum oxide

Powdered aluminum oxide

 

 

 

 

 

 

Purity of the crystal is highly important.  According to Levine, the presence of certain elements can vary drastically between suppliers, and sapphire manufacturers must exercise proper quality control.  For example, titanium (Ti) and chromium (Cr) impurities can result in pink crystals.  In nature, these impurities lead to rubies and other variations of sapphire depending on the impurity.  Levine says trace amounts of these elements must be kept below 1 ppm.  Levine includes a graphic about other elements that can cause issues including silicon (Si), potassium (K), chlorine (Cl), iron (Fe), lithium (Li), and sodium (Na).  The data was collected using glow discharge mass spectroscopy (GDMS).

Typically, a company can buy two types of raw material for crystal growth that can have impurities.  Levine says it can be purified alumina powder and/or Verneuil sapphire.  Rubicon has developed a new in-house purification process that converts the raw powder into densified pellets for crystal growth without an increase in cycle time or decrease in crystal yield. This process enables Rubicon to eliminate impurities in the alumina power that they use to make crystal.

Levine includes another useful metric for analyzing sapphire, rocking curve data obtained via X-ray diffraction.  A rocking curve helps measure various stresses in a crystal.  Levine says the width of the resulting peak is highly sensitive to strain and defects within the crystal.  A narrow peak, indicated by its full width at half maximum (FWHM) measured in arcseconds, signifies a high quality crystal free of low-angle grain boundaries and lattice strain.  A standard narrow rocking curve for Rubicon’s ES2 sapphire windows is shown below.

Sample rocking curve data from Rubicon ES2 sapphire.

Sample rocking curve data from Rubicon ES2 sapphire.

 

 

 

 

 

 

 

 

What can introduce a poor rocking curve?  Levine says that high thermal gradients, fast growth rates, and impurities contributed by the surrounding insulation can introduce defects and stress into the crystal that subsequently yield poor results in rocking curve data.  He adds that accurately controlling the temperature gradient and maintaining a stable growth interface throughout the entire process can help make higher quality sapphire.

For Further Reading

Novus Light Today, Optical-Grade Sapphire, Where Quality Matters, http://www.novuslight.com/optical-grade-sapphire-where-quality-matters_N1596.html#sthash.giGipxT1.dpuf

New Applications for Sapphire: Aerospace & Defense, Part 1 of 3

1158-69 (1)

Range of sapphire products available from Rubicon Technology including large optical windows and other shapes for aerospace and defense.

Sapphire’s unique properties make it a perfect material for high-performance applications due to its optical transparency, physical strength, resistance to abrasion and corrosion, temperature durability, chemical inertness, and bio-compatibility. As a result, it is perfectly suited for extreme environments where material durability is just as important as optical clarity.

One extreme use case is in the aerospace and defense industry where there’s a need for rugged windows for targeting pods and missile domes, most notably for the US F-35 fighter jet, that may come in contact with harsh conditions from the harsh, gritty desert with extremely high temperatures to high altitudes with extreme low temperatures.

Market research firm Yole Developpement determined that non-substrate applications for sapphire in the defense, semiconductor and other applications represent 25% of the sapphire industry revenue in a new study.  The market represents a solid growth opportunity for sapphire makers.

While there is opportunity, innovation is needed.  Sapphire traditionally has been limited to smaller shapes and sizes using traditional growth methods.  As sensor technology and applications, in defense and aerospace in particular, have evolved, the size requirements for sapphire windows have grown substantially.  One company that is innovating sapphire crystal growth is Rubicon Technology.

In a recent paper, Rubicon’s Dr. Jonathan Levine, Director of Technical Business Development, detailed how Rubicon successfully produced very large sapphire blanks using a highly modified horizontal directional solidification process. This new method, named the Large‐Area Netshape Crystal Extraction (LANCE) system is currently able to produce crystals of several different orientations. The company plans to produce sapphire windows as large as 36 x 18 x 0.8 inches.

For Further Reading

Clearlysapphire.com Blog, Opportunities for Sapphire: New Applications & Markets Explained, http://blog.clearlysapphire.com/?p=426

Clearlysapphire.com Blog, How Large Can You Go? Sapphire Windows Grow Up and Across, http://blog.clearlysapphire.com/?p=409

Rubicon Technology, Synthesis and characterization of large optical-grade sapphire windows produced from a horizontal growth process, http://www.rubicontechnology.com/sites/default/files/Synthesis%20and%20Characterization%20of%20Large%20Optical%20Grade%20Sapphire%20Windows.pdf

Opportunities for Sapphire: New Applications & Markets Explained

Rubicon Technology announced the publication of Opportunities for Sapphire, a new white paper that examines markets that leverage the highly versatile material, sapphire.  Based on research from IMS Research, the paper takes an in-depth look at the demand for sapphire in key markets including LED, semiconductor and optical.  You can find the white paper on Rubicon’s new web site at http://rubicontechnology.com/resources/papers, but here’s a look at what you’ll find.

Sapphire has emerged as a versatile material in a range of industries for many varied applications.  Sapphire’s inherent physical attributes for durability, light transmission, chemical inertness and thermal insulation make it desirable for a growing list of applications in a range of markets.  The white paper examines the opportunity for the LED market in general lighting, backlighting and display and uses in industries like automotive.  It also explores sapphire applications for optical-grade sapphire windows, lenses and covers as well as semiconductor applications such as silicon-on-sapphire chips in radio frequency integrated circuits (RFICs) for RF antennas, as digitally tunable capacitors (DTCs) and power amplifiers in smart phones and other consumer devices.

According to white paper author Jamie Fox of IMS Research, high quality sapphire delivers great benefits to LED chip manufacturers gearing up for applications like LED-based general lighting.  “Every LED company we spoke to during the research for this paper purchases sapphire and benefits from the superior yields and quality,” writes Fox.  “Substrate demand in 2012 is estimated at 42 million two-inch equivalent wafers (TIE) and expected to grow to 57 million TIE in 2013 according to market research firm Displaybank.  As the lighting market grows into a more significant segment and larger, thicker wafers are utilized, sapphire demand will accelerate.”

“Opportunities for Sapphire” also discusses the role of sapphire in LED production, the emergence of the market for large diameter sapphire wafers and sapphire demand by application.

LED Sapphire Ingot Demand Forecast

LED Sapphire Demand Graphic WPPR

(source: DisplayBank)

 

 

 

 

 

 

 

The market has shown growing demand since 2010 with an expansion of the LED/LCD TV market and the growth of applications such as general lighting.

Green line indicates rate of growth per year

Key:  Demand in thousands of millimeters of two-inch equivalent sapphire