Technology Trends

Today, we’re using basically two ways to move data in our computers. Transistors carry small amounts of data and are extremely small, while fiber optic cables can carry huge amounts of data, but are much bigger in size. Now, imagine a single technology combining the advantages of photonics and electronics. This Stanford University report says a new technology can do it: plasnomics. (For more about plasmons, read this Wikipedia article.) Theoretically, it is possible to design plasnomic components with the same materials used today by chipmakers, but with frequencies 100,000 times greater than the ones of current microprocessors. There is still a challenge to solve before getting plasnomic chips. Plasmons can only travel a few millimeters before dying while today’s chips are typically about a centimeter across. Read more…

Let’s start with some technical explanations.

Surface plasmons are density waves of electrons — picture bunches of electrons passing a point regularly — along the surface of a metal. Plasmons have the same frequencies and electromagnetic fields as light, but their sub-wavelength size means they take up less space. Plasmonics, then, is the technology of transmitting these light-like waves along nanoscale wires.

“With every wave you can in principle carry information,” says Mark Brongersma, assistant professor of materials science and engineering. [...] “Plasmon waves are interesting because they are at optical frequencies. The higher the frequency of the wave, the more information you can transport.” Optical frequencies are about 100,000 times greater than the frequency of today’s electronic microprocessors.

But let’s get back to the technology.

Plasmons are generated when, under the right conditions, light strikes a metal. The electric field of the light jiggles the electrons in the metal to the light’s frequency, setting off density waves of electrons. The process is analogous to how the vibrations of the larynx jiggle molecules in the air into density waves experienced as sound.

Plasmon waves behave on metals much like light waves behave in glass, meaning that plasmonic engineers can employ all the same ingenious tricks — such as multiplexing, or sending multiple waves — that photonic engineers use to cram more data down a cable.

This sounds good, but is it possible to use this technology today?

Because plasmonic components can be crafted from the same materials chipmakers use today, Stanford engineers are hopeful they can make all the devices needed to route light around a processor or other kind of chip. These would include plasmon sources, detectors and wires, which the lab already has made, as well as splitters and even transistors.

While an all-plasmonic chip might be feasible someday, Brongersma expects that in the near term, plasmonic wires will act as high-traffic freeways on chips with otherwise conventional electronics.

And even Brongersma recognizes that more research needs to be done before getting plasnomic chips.

The potential of plasmonics right now is mainly limited by the fact that plasmons typically can travel only several millimeters before they peter out. Chips, meanwhile, are typically about a centimeter across, so plasmons can’t yet go the whole distance.

The distance a plasmon can travel before dying out is a function of several aspects of the metal. But for optimal transfer through a wire of any metal, the surface of contact with surrounding materials must be as smooth as possible and the metal should not have impurities.

For more information, you can check the following resources.

• “Plasmonic computer chips move closer,” an article published by New Scientist on March 17, 2005
  
  
• The Brongersma Group website and its current research projects
  
  
• The abstract of a presentation given on May 21, 2005 at the March 2005 Meeting of the American Physical Society, “Sub-wavelength confinement and the diffraction limit for surface plasmon waveguides”
  

Sources: David Orenstein, Stanford University Report, March 16, 2005; and various websites

Related stories can be found in the following categories.

• Chips
  
  
• Electronics
  
  
• Future
  
  
• Materials
  
  
• Optics
  
  
• Technology
  

Transparent electronics is an emerging technology which aims to produce invisible electronic circuits. Now, researchers from Oregon report they made a major advance in transparent electronics. Their zinc-tin-oxide ‘thin-film’ materials are amorphous, physically robust, chemically stable and cheap to produce at just above room temperature. These new materials and transistors offer many new possibilities for consumer electronics, transportation, business and the military. Even if these transparent transistors don’t show up inside your next computer, they might soon appear in flat panel screens, flexible electronics devices you’ll carry with you, and even in your car windshields. But it should take some time. Read more…

Before going further, please remember that the following quotes are written in PR jargon. So read them with a grain of salt…

Researchers at Oregon State University (OSU) and Hewlett Packard have reported their first example of an entirely new class of materials which could be used to make transparent transistors that are inexpensive, stable, and environmentally benign. This could lead to new industries and a broad range of new consumer products, scientists say.

This is a significant breakthrough in the emerging field of transparent electronics, experts say. The new transistors are not only transparent, but they work extremely well and could have other advantages that will help them transcend carbon-based transistor materials, such as organics and polymers, that have been the focus of hundreds of millions of dollars of research around the world.

It’s time for more ‘technical’ details about these zinc-tin-oxide thin film transistors.

They are amorphous, meaning they have no long range crystalline order, which helps to keep processing costs a great deal lower. They are also physically robust — hard to scratch, chemically stable, resist etching, and have a very smooth surface. They are made from low cost, readily-available elements such as zinc and tin, which raise no environmental concerns.

“What has been most surprising, however, is that we can make high quality oxide transistors with these new materials at just above room temperature,” said John Wager, a professor of electrical and computer engineering at OSU. “Simply put, that’s shocking. Most integrated circuits made today, by comparison, are produced at temperatures between 700-1,100 degrees centigrade.”

As you probably guessed by now, this technology is a nascent one. But researchers are very optimistic about future uses, for example with gas sensor systems.

These sensors are used extensively in automotive and other mechanical applications, and the new zinc-tin oxide transistors might allow the creation of a new type of gas sensor whose sensitivity is electronically controlled over a wide dynamic range.

In the field of transparent applications, there should be uses in consumer electronics, transportation, business and the military. Automobile windshields could transmit visual information. Glass in almost any setting could also double as an electronic device, possibly improving security systems or transparent displays. The military is extremely interested in research of this type because of possible uses in sophisticated technology or fighting equipment.

For more information about transparent electronics, you should visit John Wager’s home page at Oregon State’s School of Electrical Engineering and Computer Science. Here is a direct link to his research activities.

The latest work done by Wager and his colleagues has been published online by Applied Physics Letters on December 23, 2004. Here is a link to the abstract of this paper named “High mobility transparent thin-film transistors with amorphous zinc tin oxide channel layer.”

A previous paper about these see-through transistors was published last year by the Journal of Physics D: Applied Physics. Here is a link to this full paper, named “Spin-coated zinc oxide transparent transistors,” from which the above illustration was extracted.

Sources: Oregon State University news release, via EurekAlert!, December 28, 2004; Applied Physics Letters, Volume 86, Issue 1, January 3, 2005; Journal of Physics D: Applied Physics, Volume 36, Number 20, October 21, 2003; and various websites

Related stories can be found in the following categories.

• Electronics
  


• Future
  


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• Science
  

A flexible image scanner that you could roll up and carry in your pocket along with your cell phone will soon help you to capture an accurate image of a curved surface such as the label on the wine bottle you just shared with friends. In “Flexible scanner works on curved surfaces,” New Scientist writes that a recently introduced prototype weighs less than 1 gram. Its dimensions are 50 by 50 millimeters and it’s only 0.4 millimeter thick. You connect it to your phone, which acts both as a power provider and as a display. So far, this flexible scanner can only capture images of its own size and has only a resolution of 36 dots per inch. But more advanced scanners should be on the market within three years, with better resolutions and in various sizes. The Japanese inventors say that a 7-centimeter-square scanner should cost about $10. Read more…

Here is the description of this flexible scanner by New Scientist.

The new device, developed in Japan by electrical engineer Takao Someya and colleagues at the University of Tokyo, comprises a polymer matrix in which thousands of light-sensitive plastic photodiodes have been deposited 700 micrometres apart beneath a grid of plastic transistors.

Each photodiode produces a current in response to light input, which its accompanying transistor stores as a charge. This can then be read into the memory of a mobile phone and converted into an image.

To use the sheet image scanner, it has to be placed on the area of interest, such as a bottle or an open book. It can only capture the image it covers; it cannot be swiped across it like an office hand scanner.

The above images were also shown in “Flexible image scanner,” published by ElectronicsWeekly.com, which adds a few details about the resolution of the device.

Each pixel in the device consists of an organic transistor and organic photodetector with an effective sensing area of 50×50µm and the 0.4mm thick imager has a 50×50mm sensing area and resolution of 36 dots per inch (dpi) “with the potential to go up to 250 dpi”, said Someya.

In this other article, “Image scanner fits in a pocket,” optics.org brings additional information.

The device consists of a polymer laminate sheet containing a two-dimensional array of light sensor cells, each featuring an organic transistor and an organic photodiode.

Unlike conventional image scanners which mechanically scan a linear array of photodetectors over an object, the new Japanese design does not require any moving parts or internal optics to capture an image. Instead, the sheet is simply placed over the target object in ambient light conditions and the transistors are probed to reveal to the light intensity of each photodetector. Each sensor cell is also covered with an opaque light shield to prevent incident light from above distorting the signal generated by the object below.

Someya’s current prototype has an effective sensing area of 2×2 inches and is just 0.4 mm thick and 1 g in weight. It features an array of 72×72 (5184) sensor cells, each 700 µm in size, giving a scan resolution of 36 dpi.

This flexible scanner was recently introduced during a presentation at the International Electron Devices Meeting (IEDM 2004), which was held in December in San Francisco. Here is a link to the press kit for this organic sheet-image scanner.

For more information, you can visit the Takao Someya Group website, which contains an abstract of the IEDM presentation.

A large-area, flexible, and lightweight sheet image scanner has been successfully manufactured on a plastic film, for the first time, integrating high-quality organic transistors and organic photodetectors. Since this area-type image-capturing device does not require any optics or any mechanical scanning devices, it is innovatively light to carry, shock-resistant and potentially inexpensive to manufacture.

Finally, I already mentioned here a previous work from the Takao Someya Group, “Flexible Sensors Make Robot Skin.”

Sources: Celeste Biever, New Scientist, December 23, 2004; Steve Bush, ElectronicsWeekly.com, December 14, 2004; Oliver Graydon, optics.org, December 22, 2004; and various websites

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• Displays
  
  
• Electronics
  
  
• Handhelds
  
  
• Optics
  
  
• Sensors