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How to understand FRAM technology, many novices are not very clear about this, in order to help you solve this problem, the following small series will explain in detail for everyone, people who have this need can learn, I hope you can gain something.

Mature semiconductor memory technologies fall into two categories:

1. RAM is random access memory with symmetric read and write access times.

2. Nonvolatile memory traditionally has been ROM (Read Only Memory) until the advent of floating gate technology. Floating gate technology has resulted in electrically erasable memories such as flash memory and EEPROM. These products allow in-system programming, but read and write access times vary. In fact, write access times may be orders of magnitude greater than read access times.

Ferroelectric random access memory or FRAM is truly nonvolatile RAM because it combines the advantages of RAM and nonvolatile memory. The write advantage and non-volatility over Flash/ EEPROM make it ideal for storing data without power.

ferroelectric properties

Ferroelectric properties are a class of phenomena

Lead zirconate titanate (PZT) and other materials. PZT has a perovskite crystal structure, as shown in Figure 1. The central cation has two equal and stable low energy states. These states determine the position of the cation. If an electric field is applied in the right direction, the cations will move in the direction of the electric field.

Applying an electric field to the crystal causes alignment of low energy states or positions in the direction of the electric field, and vice versa. Therefore, an applied electric field will cause the cation to transfer from a high energy state to a low energy state. This transition produces energy in the form of electric charge, commonly referred to as switching charge (Qs). Therefore, applying an alternating electric field to the crystal will cause cations to move from the top of the crystal to the bottom of the crystal and move again. Each conversion generates a charge Qs.

Figure 1. Ferroelectric PZT perovskite crystal

A common misconception is that ferroelectric crystals are ferromagnetic or have similar properties. The term ferroelectric refers to the similarity of the charge curve with voltage to the hysteresis loop (BH curve) of ferromagnetic materials, as shown in Figure 2. Figure 2. Ferroelectric materials switch in electric fields and are unaffected by magnetic fields.

Figure 2. Ferroelectric Hysteresis Loop

Ferroelectric materials have two states, the top cation is called "upper polarization" and the bottom cation is called "lower polarization," as shown in Figure 3. Binary memories can be generated under feasible detection schemes.

Figure 3. Two polarization states

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