Memrister technology

Memristor consists of resistor, capacitor and an inductor. Memristor, the HP device, is composed of a thin (50 nm) titanium dioxide film between two 5 nm thick electrodes, one Ti (Titanium) the other Pt (platinum). 

There are two layers to the titanium dioxide film, one of which has slight depletion of oxygen atoms. The oxygen vacancies act as carriers meant for the depleted layer has a much lower resistance than the non-depleted layer. When an electric field is applied, the oxygen vacancies drift changes the boundary between the high-resistance and low-resistance layers. When a current is applied (through the wire) to the upper layer, the vacancies are pushed into the lower level of titanium dioxide. It changes the resistance of the lower level. Thus the resistance of the film as a whole is dependent on how much charge has been passed through it in a particular direction, which is reversible by changing the direction of current. It is considered a nonionic device. Memristance is displayed only when both the doped layer and depleted layer contribute to resistance. When enough charge has passed through the memristor, that the ions can no longer move, the device enters hysteresis.4. Working

Leon Chua describes that the working of memristor is like a pipe through which water flows. The water is like the electric charge. The resistor's obstruction of the flow of charge is comparable to the diameter of the pipe: the narrower the pipe, the greater the resistance. For the history of circuit design, resistors have had a fixed pipe diameter. But a memristor is a pipe that changes diameter with the amount and direction of water that flows through it. If water flows through this pipe in one direction, it expands (becoming less resistive). But send the water in the opposite direction and the pipe shrinks (becoming more resistive). Further, the memristor remembers its diameter when water last went through. Turn off the flow and the diameter of the pipe "freezes" until the water is turned back to 0.

4.1 Boolean computation in Memristor

Digital Processor of today's computer acknowledge basic "on" and "off" states only, whereas Memristor based computer would have ability to keep in mind a variety of electrical states even after they would be switched off.

4.2 Switching behavior of Memristor

Switching behavior of memristor. (a) "ON" state, low resistance, (b) "OF" state, high resistance. The key feature of Memristor is; it can remember the resistance once the voltage is disconnected. In (a) "doped" and "undoped" regions are related to Ron and Roff, respectively. The dopant consists of the mobile charges. In (b) L and W are the thin-film thickness and doped region thickness, respectively.

4.3 Storage of Memristor

 The memristor is a new architecture that allows the stacking of multiple crossbar memories on top of each other. This allows multiple petabits of memory (1 petabit = 128TB) to be addressed in one square centimeter of space. To get a feel for how much memory this is, consider 1 terabyte is equal to 128 DVDs. Thus, we talk about a lot of power efficient storage in a very little space.

5. Applications of Memristor

Memristor modifies the circuit which will revolutionize the world. Following are the few application of the Memristor technology.

5.1 Non-Volatile Memory

Since, Memristor has an ability to retain memory states, and data in power off mode. NVRAM (Nonvolatile Random Access Memory) is the first Memristor based product we will see first, commercially. There are already 3nm Memristor in construction now. Crossbar latch memory developed by Hewlett Packard is apparently about one tenth the speed of DRAM (Digital Random Access Memory). The flash memory or solid state drives (SSD) could be commercially available within 2 years

5.2 Cross bar latches as Transistor substitute or Augmenter

The large power consumption of transistors has been a barrier to both miniaturization and microprocessor controller development. Transistor can be replaced by Memristor by combining solid state Memristor and crossbar latches which will also reduce the size of circuits.

 

5.3 Memristor Mimic neuromorphic and biological system

Electrical pulses travel through the body nervous system; they are passed from neuron to neuron. A synapse, which consists of a gap junction and the cell membranes of the transmitting and receiving neurons on either side of this gap whereas Memristor has titanium dioxide film, one of which has a slight depletion of oxygen atoms same as human brain structure and Memristor and synapses also function in a similar way: by remembering the resistance of a current passing through them, they enable memory.

6. Advantages of Memristor

• Memristor technology will reduce the overall size of computer thus minimizing the price.
• Memristor based flash memory is going to be cheaper and faster than our current flash memory and would have larger memory density. Memristor technology will replace Hard disk. Even when power is off, it'll bear in mind precisely what it had been doing and come back to work instantly as soon as computer would be turned on. This ability of Memristor makes it a replacing candidate of RAM chips too.
• .Hp Labs Memristor discovery could lead to a computer that never need to be boot up so the booting time of computer will be eliminated and we could power them down on regular basis, drastically reducing power consumption and increase the battery life.
• Memristor technology will make computers much faster and affordable for everyone.
• Memristor based computers would execute more difficult tasks because of its working with a dynamic data states in analog mode.
• Due to increase in memory speed computational power of such computers is substantially enhanced.
• Far more brain like commuting than today`s computers.
• With memristor technology computer will be able to compute those analog problems that digitally seemed impossible.
• Due to greater memory density storage volume of storage devices is increased.
• They generate less heat even though their size is smaller than transistor.   

7. Disadvantages of Memristor

• When a computer is infected with a virus or malfunctions, the Memristor could cause the computer to keep rebooting with the same issue because the memory won't be lost even after the computer reboots.
• Another problem may lie within the Memristor's ability to learn from patterns, if a foul pattern is present at an initial stage, the computer's problem might grow worse and worse in no time.

8.  Conclusion

Memristor (Memory resistor) is a passive two terminal electrical component intended as an essential nonlinear circuit element relating to charge and linkage of magnetic flux. Memristor consists of resistor, capacitor and an inductor and these are made up of TiO2 (Other materials can be used such as SiO2, but apparently TiO2 works better).Memristor has a special ability to remember "How much current has been passed through it".

There are few Memristor based products that will be expensive to be built, such as NRAM to see analog computers in market we will have to wait for a long duration of about 20 years. Memristor's ability to learn from patterns need to be used carefully because if anything goes wrong with the computer, or the computer develop a fault, it's going to be very difficult to resolve the problem.