Graphene transistors for audio amplifiers?

[jgazal]

Nobel Prize on physics caught my attention this year.

I've been reading about graphene and its peculiar proprieties.

According to Yu

[jgazal]

2075 AD.

That's too much...

[kevin gilmore]

At the rate things are going, commercial products should be available in about 10 years.

But these things along with nanotube transistors are really very low power devices

and capable of amplification in the 1ghz to 100ghz region.

[Emooze]

I'd be more excited for someone to figure out how to make diamond semiconductors less expensive.

[mypasswordis]

I should've figured someone would figure out how to dope diamond into a semiconductor. And wtf is a zero bandgap semiconductor? Wouldn't that just make it.. a conductor? I guess they didn't want to call it a 'metal'?

[jgazal]

I'd be more excited for someone to figure out how to make diamond semiconductors less expensive.

Diamond structure needs heat and pressure. That will be always expensive to create (other than the ones we scarcely find in nature and that are relatively difficult to extract). There is this, but there was no news at all since 2003.

Graphene layer needs only graphite and scotch tape (at small scale). That's pretty cheap.

Both have similar advantages for semiconductors. Worst part is mass production, but that is in charge of the semiconductor industry...

We could think organic semiconductors or quantum computers. But that does not help with audio amplifiers...

[jgazal]

I should've figured someone would figure out how to dope diamond into a semiconductor. And wtf is a zero bandgap semiconductor? Wouldn't that just make it.. a conductor? I guess they didn't want to call it a 'metal'?

This is an interesting question. It seems that metal has an overlap between energy bands instead of a zero band-gap:

Figure 1: Simplified diagram of the electronic band structure of metals, semiconductors, and insulators.

http://upload.wikimedia.org/wikipedia/commons/thumb/c/c7/Isolator-metal.svg/500px-Isolator-metal.svg.png

(...)

Figure 3: Bulk band structure for Si,Ge,GaAs and InAs generated with tight binding model. Note that Si and Ge are indirect while GaAs and InAs are direct band gap materials.

http://upload.wikimedia.org/wikipedia/commons/thumb/1/1f/Bulkbandstructure.gif/400px-Bulkbandstructure.gif.

[mypasswordis]

Hm, yeah that sounds right. Meanwhile, here's an interesting article:

Tuning a bandgap in graphene - nanotechweb.org

Varying gate voltage changes the size of the bandgap.

Direct gap and indirect gap is another property of semiconductors, separate from the size of the bandgap.

[jgazal]

At the rate things are going, commercial products should be available in about 10 years.

But these things along with nanotube transistors are really very low power devices

and capable of amplification in the 1ghz to 100ghz region.

Is that 1ghz to 100ghz region very critical?

Shall we hope for better I/V discrete stages for DAC's at least, do you think?

[jgazal]

Hm, yeah that sounds right. Meanwhile, here's an interesting article:

Tuning a bandgap in graphene - nanotechweb.org

Varying gate voltage changes the size of the bandgap.

Direct gap and indirect gap is another property of semiconductors, separate from the size of the bandgap.

Thanks for that.

[MASantos]

Is that 1ghz to 100ghz region very critical?

You know that that's waaaaaaaaaaayyyy above audio frequencies don't you?

[kevin gilmore]

I think you are both missing the point, these things really are suitable for RF frequencies only.

Unless someone can show me otherwise. DC stability on these devices is going to be absolutely

horrible, and drift with temperature is going to be significant. Plus the input impedance is going

to be way low too. Going to be great for cell phones and GPS receivers, but not for audio.

[jgazal]

Audio range: 20Hz to 20Khz (not sure how higher frequencies interact with audible frequencies; I would like to understand those furrier series…)

CD sampling: 16 bits and 44Khz.

SACD: 1 bit and 2.8Mhz.

DVD-A: 24 bits and 96Khz.

DXD: 24 bits and 352Khz.

Am I right?

Why that fellow IBM engineer is telling us that graphene transistors will improve the "fidelity of audio and video recording"?

Does he refer to higher recording samples? Better than SACD (2.8Mhz)? Is just that?

Where are we going to store that amount of data?

OR does he refer to a better DAC with higher internal clock (higher upsampling and smooth discrete analog filtering)?

The DSP engine of the Sabre™ DAC operates at either 27MHz for audio

rates up to 96KS/s or 40Mhz for audio data rates up to 192KS/s. Neither of

these rates is integer-related to the audio clock.

http://www.esstech.com/PDF/sabrewp.pdf

Then it is just better playback...

It seems odd to use an ADC with higher internal clocks and then down sampling just for transmission and storage...

[falkon]

A zero point semiconductor is a material with a band structure in which the conduction band is touching the valence band at a single point. Graphene is such a material. The reciprocal lattice of graphene is a hexagon. The bandstructure is simply 2 cones touching each other at their tip at each corner of this hexagon.

The primary method to tuning bandgap in graphene is by patterning them into nanoribbons. Additional quantum confinement in 1 direction opens a the band gap. This is similar to the effect obtained when graphene sheets are rolled into nanotubes. The band structure of nanotubes is such that we can imagine using a vertical plane to intersect the graphene bandstructure. If the intersection occurs at the corner of the hexagon, it will cut through the center of the cone, forming a zero-bandgap or metallic nanotube or nanoribbon. Otherwise, there is a gap, and it is a semiconducting nanotube or nanoribbon.

As of now, nanotubes and graphene are not viable as commercial semiconductors mostly due to difficulty in manipulating these materials. However, they are already commonly used in bulk as metallic interconnects and transparent conductors.

[jgazal]

Okay, my limited rationality has found a dead end and I would like to keep the thread alive.

On one hand, Dr. Gilmore states there will be no use for graphene transistors at the analog stages of an audio chain.

On the other hand, that fellow from IBM says graphene transistors do not work easily with discrete electronic signals (zero band gap).

If there is no use for graphene at digital or analog stages, how can graphene improve the fidelity of audio and video recording?

Exactly which component within the audio chain would improve using graphene?

Is he already foreseeing "bandgap tuning" (defeating the major roadblock)? Then it would be the digital components (basically DSP processors), right?

That first text seems so contradictory to me.