Mechanical Properties of Monocrystalline Silicon

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Monocrystalline Silicon Wafers

Monocrystalline silicon does not have grains nor domains; it is monolithic. However, it is not isotropic. Its Young modulus is different in different crystallographic directions. The strength is also different in different crystallographic directions. See below for more.

Lapped or Alkaline etched Silicon Wafer surfaces scatter light. Polished Silicon wafers are excellent reflectors of both visible and IR light. They are used for astronomic mirrors, for laser scanners and for controlled microscopic mirror arrays.

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Monocrystalline vs Polycrystalline Solar Panels

What is the difference between Monocrystalline and Polycrystalline solar panels? Watch the video below to learn!

Monocrystalline Defined

Monocrystalline silicon (also referred to as single-crystal silicon), also known as single-crystal silicon, is the core material for many silicon-based solid-state devices and integrated circuits found in most modern electronic equipment. The silicon crystals that comprise monocrystalline silicon have a unique electrical charge and orientation. This electrical charge and orientation are necessary for the operation of certain electronic devices.

Silicon is a semiconductor with two values. One side of the crystal has a positive charge while the other has a negative charge. Silicon is a rather poor conductor of electricity, but when a current is applied, it becomes a conductive metal. Monocrystalline silicon wafers are prepared by placing a crystalline structure of silicon on an electric phase with a metal binder such as ferricyanide or sodium silicate. Silicon is mixed with a suitable binder and a wafer can then be produced.

Among the most common applications of monocrystalline silicon is the use of solar cells for personal devices. The solar cells made from the material are quite effective at converting the sun's rays into electric energy that can then be used to power household appliances. Some of these devices are so efficient that they can completely replace the need for conventional solar cells. PV cells, which stands for photovoltaic cells, are often the most effective applications of the material in solar-powered devices.

PV solar cells are made by imprinting a crystalline structure of silicon onto a conductive wafer. They must be made in a precise orientation to achieve this accurate alignment. In general, the PV cell is set in a frame that is tilted at an angle of about thirty-five degrees. This tilt enables the PV cell to absorb the maximum amount of solar radiation. In addition, the wafer must be made with an orientation that ensures that the crystalline structure is able to absorb the maximum amount of sunlight for maximum conversion to electricity.

The crystals that make up the silicon wafer are also set in a specific orientation. To start, the wafer is imprinted with a perfectly flat, crystalline structure that acts like a hexagonal pattern. On one side of the wafer is then etched a hexagonal grating with alternating grooves. This design corresponds to the side of the solar cell that will accept sunlight most efficiently. On the other side of the flat wafer, a second crystal structure called a Yoke is imprinted that acts in a perpendicular manner to the first crystalline structure to ensure that energy gaps are created between each layer.

The solar cells are then manufactured and aligned on the wafers. Next, two layers of material are laid over the top of the wafers to protect and preserve the wafer structures. On one side of these layers are deposited a thin layer of monolithic material called the deposited oxide layer. This layer is highly effective at reflecting and removing any excess energy that would otherwise pass through the thin layers of crystalline material that form the base of the wafer.

To improve the efficiency of the cell, thin films of substrates are then formed on the top surface of the wafers. One of these substrates has a high degree of porosity which allows water to pass though it relatively quickly. Meanwhile, a second, thin film is placed directly below this top substrate. The surface of this second layer acts as a reflector which then captures the sun's energy. Substrates are usually made of either glass or plastic which have the properties to create the proper thickness needed to allow the light to pass through them without being absorbed.

Monocrystalline wafers are now used by a wide range of manufacturers worldwide in a wide range of applications. In the past they were primarily used for solar panels but now many manufacturers are starting to use them in a variety of applications including precision manufacturing and even computer applications. Because of their efficiency and reliability, Monocrystalline ingots are fast becoming a leading component of manufacturing processes and the technology continues to grow.

 

What are The Mechanical Properties of Monocrystalline Silicon?

A scientist asked us the following:

I also need to know how good the surface polish is over a 25mm diameter section in the dead center of the wafer in static situ? I am interested in the fineness of the grind and the flatness? Is their any grain to a wafer?

Thermal conduction properties are needed also. The end product would be a flexible reflector.
If my idea is correct it will generate a new manufacturing stream for you.

Below are the mechanical properties of monocrystalline silicon. Please send us any question.

PROPERTY VALUE UNITS
Bulk modulus of elasticity 9.8·1011 dyn/cm2
Density 2.329 g/cm3
Hardness 7 on the Mohs scale
Surface microhardness (using Knoop's pyramid test) 1150 kg/mm2
Elastic constants C11 = 16.60·1011 dyn/cm2
C12 = 6.40·1011 dyn/cm2
C44 = 7.96·1011 dyn/cm2
Young's Modulus (E) [100] 129.5 GPa
[110] 168 GPa
[111] 186.5 GPa
Shear Modulus 64.1 GPa
Poisson's Ratio 0.22 to 0.28 -


Compressive Strength 960 MPa
Tensile Strength 350 MPa
Shear Strength 240 MPa
Thermal Expansion Coefficient 2.6E-6 /ºC
Thermal Conductivity 149 W/m/ºC

monocrystalline solar panel

Note that Silicon wafers are made from monocrystalline Silicon.
Such material does not have grains nor domains; it is monolithic.
However, it is not isotropic. Its Young modulus is different in different crystallographic directions.
The strength is also different in different crystallographic directions.
A silicon wafer when bent will break along cleavage planes.
A (100) orientation wafer will break into rectangular pieces, that is into pieces with 90º angles..
A (111) orientation wafer will break into pieces with 60º angles.
A (110) orientation wafer will break into pieces with 70.5 and 109,5º angles.
The compressive, tensile and shear strengths listed are bulk values.
In monocrystalline materials they are different in different directions

Standard 4"Ø wafers have total thickness variation of <10µm. Flatness, as measured by TIR is normally <7µm and central 25mm diameter area probably has TTV <2.5µm. Specially made 4"Ø wafers can have TTV<5 or even <1µm with TIR and TTV of central 25mm diameter, proportionally smaller.

Standard lapped or fine diamond ground 4"Ø wafers have TTV<4µm (which after polishing degrades to TTV<10µm) and Surface Roughness of about 50µm.
Standard polished 4"Ø wafers have TTV<10µm but Surface Roughnss <0.5nm as measured by an Atomic Force Balance over 2×2µm area {polishing a lapped wafer degrades its TTV some but improves Surface Roughness a lot}.