Materials Science
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Muhammad Raihan
Fathoni
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Farras Zaky
Kurniawan
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Ghafira Aisyah Arfin
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Materials Science
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Muhammad Shafly
Syarif
5009231071
Institut Teknologi Sepuluh Nopember
1
Introduction
Non-metallic elements are a group of elements that have very different physical and chemical
properties compared to metals. Typical properties such as non-gloss, heat and electrical insulators,
and the ability to form covalent compounds make non-metals have an important role in various
reactions and materials. Elements such as carbon, oxygen, nitrogen, and silicon are examples of nonmetals that have many uses in life and industry.
The paper entitled Nonmetallic Properties and Optical Phenomena will discuss some basic principles
and concepts related to the nature of electromagnetic radiation and its possible interactions with solid
materials. Then, it explores the optical behaviour of metallic and non-metallic materials in terms of
absorption, reflection and transmission characteristics. Finally, it outlines luminescence,
photoconductivity, and amplification of light by stimulated emission of radiation (lasers), the practical
use of these phenomena, and the use of optical fibres in communications.
Problems
Based on the background contained in the previous slide, the problems
that will be discussed in this paper are as follows:
Problem 01
Problem 02
Problem 03
How do the materials
respond to exposure to
electromagnetic
radiation?
What are the applications
of optical properties of
non-metallic materials in
technology?
What is the optical
behaviour of metallic and
non-metallic materials in
terms of absorption,
reflection and
transmission
characteristics?
01
Goals
Knowing the response of materials to exposure
to electromagnetic radiation
02
03
Knowing the application of optical properties of
non-metallic materials in technology
Knowing the optical behaviour of metallic and
non-metallic materials in terms of absorption,
reflection, and transmission characteristics
Benefits
First
Second
Third
Improving understanding of the optical properties
of non-metallic materials
Assisting the design of non-metallic materials
for the optoelectronic industry
Supporting the development of non-metallic
material-based technologies
A non-metallic material is a type of material that does not
have the conductive properties of metals, is generally
insulating, lightweight, corrosion-resistant, and used in a
variety of structural and functional applications. Examples
include ceramics, glass, polymers, rubber and non-metal
based composites. These materials have low electrical and
thermal conductivity, and can be transparent or
translucent. Based on their electronic structure, nonmetallic
materials
fall
between
insulators
and
semiconductors with large band gaps. In amorphous or noncrystalline materials such as glass and silica, the disordered
structure creates a local energy barrier that affects optical
and electrical properties, including the appearance of
exponential absorption tails at the absorption band
boundaries.
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The interaction of light with a material depends on its electronic structure and band gap. Light can be reflected,
transmitted, absorbed or re-emitted. If the photon energy is smaller than the band gap with the light is transmitted, if
it is larger, it is absorbed and triggers an electron transition. Reflection and refraction are affected by the refractive
index and surface of the material. In amorphous materials such as a-Si, the irregular structure causes the absorption
spectrum to broaden, suitable for broad-spectrum applications although less efficient than crystalline materials.
(a) Amorphous: the atoms are arranged randomly and irregularly. Due
to the random arrangement, the energy levels become diffuse (not
discrete), causing light absorption to occur over a wider energy range.
They are suitable for applications that require broad-spectrum
absorption, such as thin-film solar cells. However, the light absorption
efficiency is usually lower than that of crystalline materials.
(b) Crystalline: the atoms are arranged regularly and periodically. It has
a regular electronic structure, so energy transitions (such as photon
absorption) occur at specific (discrete) energies. The absorption
spectrum is sharp and the light absorption efficiency is high at a certain
wavelength. Widely used in crystalline solar cells, lasers, and
optoelectronic devices.
1.
REFLECTION
Reflection when light is reflected
Light waves bounce back from
the surface of the material.
Example: Mirror or smooth
metal surface.
3.
ABSORPTION
Absorption describes the absorption
of light energy by a surface.
Example: Black surfaces absorb
more light than white surfaces.
2.
REFRACTION
Refraction when light is deflected
due to differences in refractive
index.
Example: Pencil looks “broken”
when dipped in water
4.
TRANSMISSION
Transmission occurs when light
penetrates the material. Light waves
pass through the material without
significantly changing their direction or
intensity.
Example: Clear glass allows visible light
to pass through without much
Refraction is the phenomenon of the bending of light when passing through the interface of
two mediums with different refractive indices. According to Callister, the refractive index is
defined as the ratio of the speed of light in vacuum (c) to the speed of light in the medium
(v), which is written as:
This refractive index is influenced by the wavelength of light. In metal materials, the refraction
phenomenon occurs in complex conditions because the refractive index is complex.
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Reflection is the reflection of light waves on the surface of a material. In metals, most of the
light will be reflected because of the presence of free electrons that are able to oscillate when
exposed to the electromagnetic field of light waves.
According to Callister, reflectivity (R) is defined as the fraction of light intensity reflected on
the surface of a material:
With :
Ir : Intensity of reflected light
I0 : Intensity of incident light
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Absorption is the phenomenon of absorption of light energy by a material. In metals, free electrons absorb electromagnetic wave
energy and convert it into heat energy.
The phenomenon of absorption in metals depends on:
Light Frequency: At high frequencies (such as ultraviolet light), the energy absorbed is greater.
Type of Metal: The energy band structure and electronic properties of the metal determine the absorption capacity.
Callister explains that for absorption to occur, the photon energy (hν) must be greater than the band gap energy (Eg):
If the photon energy is less than Eg​, the light will be reflected or transmitted, not absorbed. In metals, the
photon energy is sufficient to excite free electrons, so that visible light is absorbed and converted into heat.
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Transmission is the process by which light enters a material and successfully passes through
it to exit on the other side without being completely absorbed or reflected by the material.
So, if a light falls on the surface of a transparent object, some of it may be reflected, some
absorbed, and the rest transmitted to the other side. This process is explained using
mathematical equations that include the effect of material thickness and absorption
coefficient on the intensity of light transmitted:
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Color in transparent materials arises as a result of selective absorption of certain wavelengths of light from the
visible light spectrum. When white light (which contains the entire visible color spectrum) passes through a
transparent material, some wavelengths of light are absorbed, while the rest are transmitted. The color we see
in the material is a combination of the wavelengths of light that are transmitted, not absorbed. If all
wavelengths were absorbed equally, the material would appear colorless (clear or fully transparent), as in
ordinary glass or pure sapphire.
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Opacity and translucency in insulators especially dielectric materials are strongly influenced by the
material's ability to reflect, refract and transmit light. Although many dielectric materials are intrinsically
transparent, internal reflection and refraction phenomena can cause incoming light to be scattered,
making it appear hazy or even opaque. Opacity occurs when the scattering of light is so great that almost
no light is transmitted straight through the material.
One of the main causes of translucency and opacity is
porosity. Porosity is a measure of how many voids or
pores (empty spaces) there are in a material. Ceramic
materials that have pores left over from the fabrication
process will scatter light significantly. An example can be
seen in the figure, which shows the light transmission in
three types of aluminum oxide specimens: single crystal
(transparent), dense polycrystalline (translucent), and
porous polycrystalline (5% porosity) that appears opaque.
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Luminescence:
Emission of light from
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z
due to electron excitation and
relaxation.
Types (by excitation source):
Photoluminescence (light),
Electroluminescence (electricity),
Chemiluminescence (chemical),
Radioluminescence,
Cathodoluminescence
Based on light emission time:
Fluorescence: Fast emission (<10⁻⁸ s)
Phosphorescence: Slow emission via
metastable state
Applications:
Fluorescent lamps (UV to visible light)
Bio-imaging (cell labeling)
Anti-counterfeit security (UV inks)
Sensors (gas, chemical)
Mechanism: Electrons excited to higher energy → return to ground state → emit photons
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Increased electrical conductivity
z
in a semiconductor
upon light
exposure
Key characteristics of photoconductors
include:
Spectral response: Determines the range
of light wavelengths the material can
absorb.
Photoconductive gain: The ratio of the
number of charge carriers generated to
the number of absorbed photons.
Response time: The speed at which
conductivity changes when light is applied
or removed.
How it works:
1. Photon absorbed →
2. Electron promoted to conduction band →
3. More charge carriers →
4. Higher current
Some photoconductors :
CdS → LDR (visible light)
PbS, InSb → IR sensors
a-Si → cameras, solar cells
Applications:
Automatic lighting
UV/IR/X-ray detection
Optical switches
Light-controlled electronics
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A Light Emitting Diode (LED) emits light via
z a p-n junction under
electroluminescence at
forward bias
White LED technology uses blue GaN LEDs with yellow phosphor
or RGB LEDs to create full-spectrum light, known as pc-LED.
Electron-hole recombination → photon emission
Applications:
Lighting (homes, industries)
Displays (TVs, smartphones)
Traffic & automotive lighting
Medical and agriculture
Optical fiber communication
Conclusions
1
The paper, Nonmetallic Characteristics
and Optical Phenomena, reviews some
key principles and ideas relating to the
nature of electromagnetic radiation and
its potential interaction with solid
materials. Next, it explores the optical
behaviour of metallic and nonmetallic
materials in the context of absorption,
reflection, and transmission features.
Finally, it explains luminescence,
photoconductivity, and light gain
through stimulated emission of
radiation (lasers), practical applications
of these phenomena, and the use of
optical fibres in communications.
2
In the applications section, the paper
outlines that a number of optical
phenomena such as luminescence,
photoconductivity, and light ejection
(electroluminescence) have been
utilised in innovations in LEDs, light
sensors, biological imaging, and
counterfeit-resistant inks. Amorphous
semiconductor materials such as
amorphous silicon (a-Si) are also
indicated to have benefits in broad light
absorption, thus making them
promising materials for thin-film type
solar cells, despite their lower
luminescence efficiency compared to
crystalline semiconductors.
3
Through a detailed comprehension of
the microstructure and electronic
properties of non-metallic materials,
optical technologies such as energyefficient lighting and light-based
communication systems can be
optimally developed. Therefore, the
interaction of light with non-metallic
materials is not only a purely physical
phenomenon, but also a major
foundation in modern materials
engineering and technology.
THANK YOU!
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19