Solving Ge-Si Alloy & Doping P in Si - Question 6

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In summary: Use the atomic mass to convert from grams to moles, and then use the atomic percent or weight percent equations as needed.In summary, the conversation discusses a question about calculating the number of germanium atoms in a Ge-Si alloy with a specific ratio, as well as determining the weight and atomic percent of phosphorus in a silicon material. The conversation also mentions the use of density and Avogadro's number to solve the problem, and suggests referring to the first chapter of Callister's book for more information on atomic and weight percent calculations.
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fredrick08
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Homework Statement


Question 6. Germanium forms a substitutional solid solution with silicon.
(a) Compute the number of germanium atoms per cubic centimetre for a Ge-Si alloy that contains 25 w/o Ge and 75 w/o
Si.
(b) If, instead, phosphorus is added to Si to dope the material n-type at a doping of 1018/cm3, determine both the w/o and
a/o of P in the Si.

I have no idea how to do this question, what the question wants me to do, or w/o and a/o even mean. Can anyone can please put me on the right track, or even a track for starters, as this stuff is completely new to me and I have no idea. Not even where to start. Any help much appreciated, I have callister 7ed. if anyone knows where to find it, in that book.
 
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  • #2
Weight percent and atomic percent, presumably. That's all in Callister
 
  • #3
You can find the mass density of the elements. You know Avogadro's Number.

Use the density definition of mass over volume.
 
  • #4
ok, i got told this today... sorry i have no idea what avagadros number is... i looked it up, and something to do with chem... I've never done this before... ok, density is mass over volume, yes... mass am i meant to know this? get it from the table of elements? ge is 32 and si is 14... is that their mass? in that atomic u unit? then how am i meant to find the volume?? are they in a box or something?? I just don't know... could you maybe tell me, where in the book, i mite find examples of this? because our lec notes are awful, very vague... and i have no prior knowledge of chem what so ever.
 
  • #5
If you have Callister, read the first chapter. Atomic percent is the number of atoms of the solute divided by the total number of atoms. Weight percent is the weight of the solute divided by the total weight. The atomic mass is the number of grams per mole of an element (i.e., per Avogadro's number of atoms of the element).
 

FAQ: Solving Ge-Si Alloy & Doping P in Si - Question 6

What is the purpose of alloying Ge and Si?

Alloying Ge and Si is done to alter the properties of the Si crystal, making it more suitable for various electronic applications. These include increasing carrier mobility, reducing leakage current, and improving thermal stability.

How does doping P in Si affect its conductivity?

Doping P in Si introduces additional charge carriers, making it a p-type semiconductor. This results in an increase in conductivity compared to pure Si, as P atoms have one less valence electron than Si and create "holes" in the crystal structure that act as charge carriers.

What techniques are commonly used to create Ge-Si alloy and dope P in Si?

Ge-Si alloy can be created through several techniques, including physical vapor deposition, molecular beam epitaxy, and chemical vapor deposition. Doping P in Si can be achieved through ion implantation or diffusion processes.

What are the potential applications of Ge-Si alloy and P-doped Si?

Ge-Si alloy and P-doped Si have a wide range of potential applications in the field of electronics. These include high-speed transistors, solar cells, and optoelectronic devices such as LEDs and detectors.

What challenges are involved in creating high-quality Ge-Si alloy and P-doped Si?

Creating high-quality Ge-Si alloy and P-doped Si involves numerous challenges, including achieving uniform composition, minimizing defects and impurities, and controlling the diffusion of dopants. The high melting point of Ge can also make it difficult to alloy with Si without causing lattice strain and defects.

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