惠普发现忆阻器机制有望商用

惠普(HP)资深院士，也是忆阻器的发明者Stanley Williams表示，一些对于HP忆阻器的开关速度能比DRAM快，且资料保存时间能比闪存更长数百万倍等特性抱持怀疑的工程师们，现在不必再担心了。

“我们发现电场和电流可共同运作，让存储元件能够同时非常迅速地开关并无限期地保持其状态，”Williams说。“不仅仅在元件内施加电压以驱动氧空穴(oxygen vacancies)的迁移，同时间内电流也会加热到300℃──这恰好足够让非晶薄膜转化为结晶薄膜。

忆阻器被视为未来的'通用存储器'，因为它们的运作速度能与DRAM一样快，尺寸和闪存一样小，而耐用性则媲美只读存储器，据惠普表示。作为继电阻、电容和电感之后的第四种基础被动电路，忆阻器凭借在氧化薄膜中导入或移除氧空穴的属性，能够仅保留高或低电阻状态。

以同步X光在100nm具有密集氧空穴的区域内探测忆阻器(图右蓝色部份)，此即为忆阻器开关之处。围绕此一区域，新开发的结构相(红色部份)也发现类似温度计的作用，它可呈现当元件在读取或写入时会变得多热。

使用该公司最喜欢的结构──氧化钛──惠普最近还采用了高能同步X光来关联元件的电气特性及其原子结构、化学和温度。迄今有关接近底部电极的热点在开关期间能否加热到足够诱导氧化物结晶仍未有定论。在1~2nm厚的区域中驱动空穴(a 1)或传导它们(a 0)后，该薄膜以类似退火的工艺冷却，这让该薄膜保持固定结晶态，而且应该能继续保持下去。

“在测试过程中，我们让这些元件进行了超过300亿次的开关和计数，其保留信息的能力也未见衰退，”Williams说。

惠普目前正与Hynix半导体公司共同开发基于忆阻技术的商用存储器。

点击参考原文：HP discovers memristor mechanism

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HP discovers memristor mechanism

R. Colin Johnson

Electrical engineers who expressed skepticism that Hewlett Packard Co.'s memristors could switch as fast as DRAM and yet retain their memories millions of times longer than flash can now rest easy, according to their inventor, senior HP Fellow Stanley Williams.

"What we have discovered is that an electric field and a current act together to enable a memory device that can both be switched very rapidly and hold its state indefinitely," said Williams. "Not only does an applied voltage drive the migration of oxygen vacancies in the device, but at the same time there is a current that heats it up to about 300 degrees Celsius—just enough to turn the amorphous film into a crystalline film."

Memristors are touted as the future "universal memory" device because they are as fast as DRAM, as small as flash, and as durable as read-only-memories, according to HP. As the fourth fundamental passive circuit element—after resistors, capacitors and inductors—memristors retain either a high- or low-resistance state by virtue of introducing or removing oxygen vacancies in oxide thin films.

Synchrotron x-rays probed the memristor in a 100 nanometer region with concentrated oxygen vacancies (right, shown in blue) where the memristive switching occurs. Surrounding this region a newly developed structural phase (red) was also found to act like a thermometer revealing how hot the device becomes when read or written.

Using their favorite formulation—titanium oxide—HP recently used high-energy synchrotron x-rays to correlate the device's electrical characteristics with its atomic structure, chemistry, and temperature in three dimensions. The until now unforeseen conclusion was that a hot spot near the bottom electrode heats enough during switching to induce a crystallization of the oxide. After driving out vacancies (for a 1) or introducing them (for a 0) in one-to-two nanometers thick region, the film cools in an annealing-like like process which leaves the film in a fixed crystalline state that should remain that way indefinitely.

"In testing, we have switched these devices over 30 billion times and counting, with no degradaton in their ability to retain information," said Williams.

HP is currently working with Hynix Semiconductor Inc. to create commercial memories based on memristive technology.