Headline, November12, 2013

'''ONE DAY -THIS DECADE- 

ALL YOUR PRESENT TECHNOLOGY​: 

OBSOLETE''​'

Well time enough to be saying bye-bye to your flash memory in smartphones, cameras and laptops. And here is why:

As you all know, a tidy bedroom is very different from a messy one. The number of items in the room may exactly be the same, but the difference between orderly and disorderly arrangements is immediately apparent.

Now imagine a house with million rooms, each of which is either tidy or messy. A robot in the house can inspect each room to see which state it is in. It can also turn a tidy room into a messy one -by throwing on the floor at random-  and a messy room into a tidy one  -by tidying it up.

This, in essence, is how a new class of memory chip works. It is called  ''phase-change memory''  and, like  the flash memory that provides storage in mobile phones, cameras and some lap tops, it can retain info even when the power is switched off.

But it promises to smaller and faster than flash, and will probably be storing your photos, music and messages within a few years. This technology relies, as its name suggests, on special substances called phase change materials(PCMS).

These are materials, such as salt hydrates, that are capable of storing and releasing large amounts of energy when they move from a solid state to liquid state and back again. Traditionally, they have been used in cooling systems, and more recently, in solar-thermal power stations. where they store heat during the day and can be released to generate power at night.

But for memory devices it is not their their thermal properties that make PCMS so attractive. Instead it is their ability to switch from a disorderly (amorphous) state to an orderly (crystalline) one very quickly. 

PCM memory chips rely on glass like materials called chalcogenides, typically made of a mixture of germanium, antimony and tellurium.

Each cell in the memory chip consists of a region of chalcogenide sandwiched between two electrodes. The bottom electrode is a resistor that heats up when a current passes through it. 

Delivering a gently pulse of electrical energy to the cell turns on this tiny heater and causes the chalcogenide to melt.  

As it cools it forms an orderly, crystalline structure. This state corresponds to the memory cell storing a ''1''. Applying a shorter, stronger pulse of energy to the cell melts the chalcogenide but does not allow crystals to form as it cools. Instead, the region of the material above the bottom electrode assumes a disorderly amorphous state, corresponding to the cell storing a ''0''.

The amorphous state has a higher electrical resistance than the crystalline state, allowing the value store in the cell to be determined. For this reason PCM memory is sometimes called  ''resistive memory'' and the individual cells are sometimes referred at as  ''memristors''.

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!!! ''' The Great Exchange !!! '''

Good Night & God Bless!

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