nanosurface 2008-05-06 02:28
纳米力学振荡器的出现有望导致新型电子计算机
[b][size=3]'Nanomechanical Oscillators' Could Lead to New Class of Computers[/size][/b]
[b][color=Blue]【纳米科技世界快讯】More than 50 years ago, a graduate student in Japan conceived the “Parametron,” an electrical circuit that could form the basis for digital computers. The concept ultimately fell flat, but recently a pair of scientists gave new life to the idea, and their work could be a first step toward a nanomechanical computer that is based on mechanical rather than electrical operations.[/color][/b]
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[color=DimGray]A schematic drawing (top) and scanning electron microscope image of the nanomechanical oscillator. Figure courtesy Imran Mahboob.[/color]
Rather than today's electronic “0” and “1” bits—the most basic pieces of information a computer can store, defined by whether a transistor has a zero or non-zero voltage across it—the Parametron used the response of an electrical oscillator to an applied frequency. The Parametron could only oscillate in two ways, a behavior that was exploited to represent 0's and 1's to enable binary logic.
Computers based on the Parametron were built, but the idea never took off as there were difficulties with power consumption and integration, and the much faster transistor quickly rendered it obsolete.
In the era of nanotechnology, the Parametron has been resurrected using mechanical oscillators. The scientists who have revived its spirit are Imran Mahboob and Hiroshi Yamaguchi of the NTT Corporation in Japan. Their electromechanical oscillator has a bridge-over-gap structure, and it's tiny: The gap is four micrometers deep and the bridge is 260 micrometers long, 84 micrometers wide, and 1.35 micrometers thick.
The bridge and the larger piece of material that contains the gap are made of the widely used semiconductor gallium arsenide (GaAs).
At the each end of the bridge, known as clamping points, there is a sandwich structure: a thin GaAs layer between a gold electrode and a “two-dimensional electronic system,” a general term for a material in which the electrons are confined to a plane.
When an alternating-current voltage that matches the bridge's natural frequency is applied across it, the bridge will oscillate vertically. This physical motion is due to a chain of events that begins with a displacement of atoms in the thin GaAs layer in response to the voltage. This causes the positive and negative charges in the layer to separate, which, in turn, produces a strain across the length of the bridge. The bridge bends slightly, a movement that can be tuned to a resonance frequency—there are more than one—by adjusting the voltage.
These resonance modes can be used to store information as bits. For example, neighboring oscillators with resonances that differ in phase—meaning they do not oscillate in unison—can represent 0 and 1 values.
“This is a highly tunable system, which we expect will make it easily integrable into complex architectures,” says Imran.
A nanomechanical computer based on his and Yamaguchi's concept would likely never be as fast as a transistor-based computer. But it would have some advantages, including being more resilient to electromagnetic shock and more energy efficient. This could make it a good replacement for computers that do not need to be ultra-fast, such as those in appliances, mobile phones, and cars.
Citation: I. Mahboob and H. Yamaguchi Nature Nanotechnology advance online publication, 13 April 2008 (DOI:10.1038/nnano.2008.84)
来源： PhysOrg.com.
punkx 2008-05-06 12:05
日本NTT公司的两名科学家发明了一种微型机械振荡器,它可以表征0和1,从而有望成为纳米计算机的基本元件.研究结果刊登于近期的《自然-纳米技术》在线版.
这种振荡器呈桥型,尺寸很小,桥下的沟深4微米,桥长260微米,宽84微米,厚1.35微米,主要材料是目前广泛应用的半导体砷化镓.桥端的箝位点为三明治结构:砷化镓薄层位于金电极和“二维电子系统”之间.
当把符合桥的固有频率的交流电加诸其上,桥会垂直地振荡.其原理是:交流电导致砷化镓薄层中的原子错位,进而使薄层中的正负电荷分离,产生一个张力,使桥微微弯折.通过调节电压,这一运动可转化为共振,共振模式可用来存储比特信息.比如临近的振荡器共振相位不同,便能够代表0和1.
以机械操作而非电子操作实现计算,这一概念在50年前就已被提出.由于晶体管计算机迅速发展,它一度被淡忘,NTT研究人员的发明重新引发了对机械计算机的兴趣.用机械元件搭建出的纳米计算机的运行速度很可能不如晶体管计算机那么快,但也有其优点,与晶体管计算机相比,纳米机械计算机更不怕电磁冲击,更节能,可应用于无需快速计算的领域,比如移动电话和汽车.