By: Yoshimi Anzai, MD

I am wondering if you are using any reference capacitor like in the figure when you are characterizing the ferroelectric capacitor? From the capacitance information how do you extract the polarization (P)? And last question is what do you do with inductance of a ferroelectric capacitor, does it tell anything?

thanks.

Gain medium is that the material which has a suitable energy level scheme for population inversion. Laser gets amplified within the material. So we call it "gain". So if any new material with such a scheme, and the upper level lifetime for electrons is comparable to the lower level lifetime, it may be suitable for laser. And usually, in semiconductor lasers, people just use several layers of different depositions to form the gain layer and resonant cavity layer.

On the other hand, in the presence of an acceptor (p-type case), the absence of an electron will create a new set of states very close to the valence band. Electrons in the valence band can be thermally excited up into these new allowed levels, creating empty states, or holes, in the valence band. The excited electrons are stuck at the boron atom sites and act as fixed negative charges, localized there.

The images are oversimplified but, still, I believe they give a very vivid representation of each case.

By the way, good page!

Would you introduce briefly how polarization is achieved within LCD? And which material is applied?

I uploaded four files to this page. Please see the attached files. Thanks!

When you apply a sinusoidal AC electric field to the material with nonlinear dielectric properties, for example, PVDF. You would not receive the current signal in the sinusoidal shape. However from which, you can decompose and regard this curve as the sum of a few sinusoidal waves with different frequency (I am not sure if this is the double frequency as you said.). The reference 13 in this page is one of the example of how to measure the dielectric properties. I have a few more papers related to the dielectric properties of PVDF. I will upload it to this page. I hope they will be helpful.

Thank you for your comments!

-Vin

Power of pulses of several ns is very huge. But the total energy can still be very small since the pulse is really short. So these lasers would deposit the energy for a period of time and them emit it. So the input power is not large.

Ns is really a new time scale for ultrafast lasers. Previously, people can only achieve ps pulses. But I think people are still working on shorter pulses, because of the need for a strong output power in research and national defense. Maybe it is the limitation now. But not in the future.

Great Job…was just wandering if there was any other materials out there that produced the same effect that iron oxide has. Because nanoparticles can be dangerous for the body, is there any other application that iron oxide can be used for.

http://www.boston.com/news/globe/health_science/articles/2005/03/01/whose_idea_was_it/

-Vin

I think Two of the major reliability concerns hampering the use of ferroelectric thin films in non-volatile memory devices are fatigue and imprint. Fatigue consists in the loss of remnant polarization with cumulative switching of the capacitor. If the remnant polarization falls below the detection threshold of the device, the memory cell becomes unreadable.

And the hysteresis loop will show deviations when it under stressed for a long time, The fatigue in ferroelectric films is mainly due to the pinning of domain walls by space charge near the boundaries of electrodes and structural defects such as microcracking and porosity. So, if you wanna have a good non-volatile memories you do have to consider the fatigue effect on the ferroelectric thin film.

I am wondering if the hysteresis loops show deviations as a ferroelectric capacitor is electrically stressed continuously (endurance) and a very long time after they are stressed (retention). Do you thing this properties are enough to use them as non-volatile memories which requires more than 10⁶ cycles and more than 10 years of retention.

Thanks.

I have read a few papers where they utilize excimer and YAG lasers, and one thing i have notice that these lasers are pulsed (~ns) instead of running them continuously (researchers were trying to melt silicon with them). My question is: are these small time scales limitation of the lasers or are they trying trying to avoid dumping too much power?

Thanks.

I included a reference to your page where I mentioned work functions of metal-oxide-semiconductor stack.

I want to make a comment on yours: reverse bias current of a diode does not continue constant as reverse bias increasing negatively. After a certain point, diode breaks and current blows up due to two main mechanisms:

- impact ionization due to high energy (hot) electron diffused from p-side into the depletion region. These electrons have capability of knocking down more electrons and this process can yields an avalanche breakdown [Maria shows reversed biased diode in the paper] —> this process might damage the device.

- electrons in the p-side see a lower energy on the n-side's conduction band and band-to-band tunneling occurs (Zener breakdown). Since breakdown voltage for this case can be large (in the order of bandgap of the material used), this diode can be used in rectifier circuits in reverse bias.

Thanks.

Nice page,

I have a question: in the second paragraph of the "connection to an external load" part, it is stated that "From the equivalent circuit it is evident that the current produced by the solar cell is equal to that produced by the current source, minus that which flows through the diode, minus that which flows through the shunt resistor…"

My question is: How does its equivalent circuit look like and why is there a shunt resistor?

Thanks.

I hope I answered your question:)

If you change the current on the Peltier effect you will change your delta T, changing the polarity of your current you will change the direction of the thermoelectric current, but if you leave your current constant you will keep a constant delta T. For the Seebeck effect, the change in temperature will give you a current, if the delta T increase your current increase too.

Gokhan.