(Nanorush 2024) How LEDs are Made : The Journey from Start to Bright!

Summary

Drin Abdullah, a scientist at the Institute of Nano-Opto Electronics Research and Technology at University Science Malaysia, discusses the fascinating world of LEDs (Light Emitting Diodes). He explains how LEDs are used in everyday devices and how they are more energy-efficient compared to traditional lighting. He delves into the structure, composition, and fabrication process of LED chips, focusing on materials like gallium nitride, and their role in generating blue light. The process involves intricate steps like deposition, photolithography, and etching, all aimed at creating efficient light sources for a sustainable future.

Takeaways

• 💡 LED technology is essential in daily life, powering devices like smartphones, laptops, smartwatches, and even cars.
• 🌍 About 25% of the world's electricity is used for lighting, making energy-efficient lighting technologies, like LEDs, critical.
• 🔦 LEDs have various applications, from home lighting to public transport, traffic lights, entertainment, and even indoor gardening.
• 🟨 The yellow square components inside an LED bulb are LEDs, with the yellow phosphor layer converting blue light into white light.
• 🔵 Many white LEDs actually emit blue light, which is then transformed into white light by the phosphor layer on top.
• 📏 The structure of an LED is made up of multiple layers, including metals and semiconductors like gallium nitride, which emits blue light.
• 🔬 Gallium nitride layers can be adjusted to emit different colors of light, including green and ultraviolet, by modifying the indium content.
• 🏭 LED production involves a complex fabrication process, including wafer growth, metal deposition, photolithography, and etching.
• 📐 Precise control of layer thickness, temperature, and materials is essential for producing high-quality LED chips with efficient light output.
• 🌟 In 2023, the institute developed a highly efficient white LED that exceeded industry standards, producing over 200 lumens per watt.

Q & A

What is Dr. Drin Abdullah's research focus?

Dr. Drin Abdullah's research focuses on optics and photonics, with a specific interest in photonic devices such as light-emitting diodes (LEDs).

How much of the world's electricity is used for lighting?

About a quarter of the world's electricity is used for lighting, which is a significant portion of global energy consumption.

What are some common applications of LEDs mentioned in the talk?

LEDs are used in lighting homes, streets, car headlights, public transport, traffic lights, stage lighting for entertainment and sports, and even as artificial sunlight for growing vegetables indoors.

What is the primary component inside an LED bulb that produces light?

The primary component inside an LED bulb that produces light is the LED chip, which is often made from a synthetic semiconductor material like gallium nitride (GaN).

How does the phosphor layer in an LED bulb contribute to the light production?

The phosphor layer absorbs blue light emitted by the LED chip and converts it into yellowish light. The combination of blue and yellow light creates the white light we see.

What are the two common types of LED packages mentioned?

The two common types of LED packages mentioned are SMD LEDs (Surface Mount Device) and DIP LEDs (Dual In-Line Package).

What is the role of the multiquantum well (MQW) layer in an LED?

The MQW layer is the region where positive and negative charge carriers recombine, efficiently producing light. The composition of the MQW layer determines the color of the emitted light.

What are some materials used in the electrodes of an LED chip?

The electrodes of an LED chip are typically made from metals like chromium, nickel, gold, and titanium, which allow for the flow of charge in the LED chip.

What is the significance of the MOCVD process in LED manufacturing?

The Metal Organic Chemical Vapor Deposition (MOCVD) process is crucial in growing high-quality semiconductor layers, such as gallium nitride (GaN), with precise thicknesses and compositions. This process is essential for producing efficient LEDs.

How do LEDs compare to traditional tungsten lamps in terms of efficiency?

LEDs are much more efficient than tungsten lamps because they primarily produce light instead of heat. In contrast, tungsten lamps generate light by heating a filament, which results in a significant loss of energy as heat.

Outlines

00:00

💡 Introduction to Drin Abdullah and the Importance of LEDs

Drin Abdullah, a scientist at the Institute of Nano, Opto Electronics Research and Technology, University Science Malaysia, introduces himself and his work in optics and photonics. He explains the widespread use of light-emitting diodes (LEDs) in everyday devices such as smartphones, laptops, and cars. Abdullah highlights the energy consumption from lighting, noting that about 25% of the world's electricity is used for lighting. He stresses the importance of efficient lighting technologies like LEDs in reducing energy costs and consumption.

05:00

🚗 Applications of LEDs

Abdullah describes various LED applications, from lighting homes and streets to powering car headlamps and traffic lights. He also mentions LEDs used in entertainment and sports venues. Fascinatingly, LEDs are used as artificial light sources for growing indoor vegetables, showcasing their versatility. Abdullah emphasizes the need for energy-efficient technologies like LEDs to reduce the cost of lighting and energy consumption.

10:01

🔧 Inside an LED Bulb

Abdullah takes a deeper look into the structure of an LED bulb. He explains that the plastic cap (diffuser) spreads light, and beneath it lies multiple yellow-colored square components, each representing an LED. The yellow material is called phosphor, which absorbs blue light and emits yellow light. This combination produces white light. He further explains that white LEDs are essentially blue LEDs with a phosphor layer and describes two common types of packaged LEDs: SMD (Surface Mount Device) and DIP (Dual In-line Package) LEDs.

15:04

🔬 Structure of an LED and Semiconductor Materials

This section explores the structure of LEDs and the materials involved in their design. Abdullah explains that LEDs consist of metal, semiconductor, and insulator materials. The chip design includes layers of gallium nitride (GaN), a synthetic semiconductor that emits blue light. By adding different elements like magnesium and silicon to the GaN layers, the LED can generate positive and negative charge carriers, enabling light emission. The multiquantum well (MQW) layers in the chip determine the color of light, which can be fine-tuned by adjusting indium composition.

20:06

⚙️ Comparison with Tungsten Lamps

Abdullah compares the efficiency of LEDs with traditional tungsten lamps. He explains that tungsten lamps generate light by passing current through a resistor (tungsten wire), which produces light as the wire heats up. However, most of the energy is wasted as heat, making tungsten lamps highly inefficient. In contrast, LEDs efficiently produce light through the recombination of charge carriers in the semiconductor layers.

🏗️ LED Fabrication Process: Overview

Abdullah introduces the complex fabrication process of LEDs in an advanced laboratory. The process begins with LED structure development using Metal Organic Chemical Vapor Deposition (MOCVD), where layers are grown on a substrate like a layered cake. He discusses the importance of precision in monitoring, temperature control, and purity of materials during the growth process. These factors ensure defect-free, high-quality semiconductor layers needed for efficient LEDs.

🧪 Deposition, Photolithography, and Etching Processes

This section delves into specific stages of LED fabrication. Abdullah describes the deposition process, where thin layers of materials are added to the GaN layer using electron beam evaporators. He also explains photolithography, a process that uses light-sensitive polymers to create patterns on the wafer. The etching process, which removes unwanted material to form the desired LED structure, is also introduced. These processes are critical in shaping and preparing the LED chip for further stages.

🔬 Advanced Etching and Electrode Creation

Abdullah continues the fabrication process by detailing how the LED wafer is etched using inductively coupled plasma (ICP) to expose specific areas for metal electrode deposition. He explains the creation of negative and positive electrodes for the LED and describes how precision is necessary in placing metal contacts using techniques like photolithography and deposition. These steps ensure the LED functions properly when voltage is applied.

🔥 Metalization and Finalization of the LED Chip

The final steps of LED fabrication involve metalization, where the deposited metal contacts are heated to improve electrical conductivity and enhance the interface quality between the metal and semiconductor layers. Abdullah explains that this process reduces contact resistance and improves the LED's overall performance and reliability. He concludes by showing a cross-section of a completed blue LED chip, which efficiently lights up when voltage is applied.

🎓 Conclusion and Final Thoughts

In the final section, Abdullah summarizes the LED fabrication process and expresses hope that the audience has learned valuable insights about LED technology. He thanks the viewers and wishes them success in their future endeavors.

Keywords

💡LED (Light Emitting Diode)

An LED is a semiconductor device that emits light when an electric current passes through it. It is a crucial component discussed in the video, as the entire narrative focuses on the structure, manufacturing, and efficiency of LEDs. Examples from the script include their applications in everyday devices like smartphones, cars, and household lighting, as well as their use in advanced technologies for energy-saving solutions.

💡Phosphor

Phosphor is a material that absorbs light of one wavelength and re-emits it at another wavelength. In the context of LEDs, it is used to convert blue light emitted by the LED chip into white light by emitting yellow light when excited. The script mentions phosphor as the yellow-colored layer in LEDs, which helps create a white light when combined with the blue light emitted by the chip.

💡Gallium Nitride (GaN)

Gallium Nitride is a synthetic semiconductor material used in the construction of LED chips to produce blue light. It plays a central role in LED manufacturing, as highlighted in the script, where it is described as being crucial for generating efficient blue light. The script also explains how varying the composition of gallium nitride layers allows for the production of different colors, including UV light.

💡Semiconductor

A semiconductor is a material that has electrical conductivity between that of a conductor and an insulator. It is used in electronic devices like LEDs due to its ability to control electrical current flow. The video frequently refers to semiconductors such as gallium nitride, explaining how different types (p-type and n-type) are combined in LED structures to generate light.

💡P-Type and N-Type Layers

P-type and N-type layers are types of semiconductors used in LEDs. P-type layers have a higher concentration of positive charge carriers (holes), while N-type layers have a higher concentration of negative charge carriers (electrons). In the script, these layers are created by doping gallium nitride with different elements and are essential for creating a junction where positive and negative charges meet to emit light.

💡Multiquantum Well (MQW) Layer

The MQW layer is a critical part of an LED's structure where electrons and holes recombine to produce light. The script emphasizes its role in determining the color of the light emitted by adjusting the composition of indium in the MQW layers. This layer is crucial for achieving different light emissions, such as blue, green, or even ultraviolet, making it a key point of discussion in the video.

💡Metal Organic Chemical Vapor Deposition (MOCVD)

MOCVD is a technique used to grow thin layers of semiconductor materials, such as gallium nitride, by depositing atoms onto a substrate. The script likens this process to baking a multi-layered cake, highlighting its complexity and precision. It is the initial step in the LED fabrication process, where high-quality layers are grown under controlled conditions to form the base of LED chips.

💡Deposition

Deposition refers to the process of adding thin layers of material onto a surface. In LED manufacturing, deposition is used to place semiconductor and metal layers onto the LED wafer. The video mentions several deposition techniques, such as using an Electron Beam Evaporator, to create indium oxide layers and metal contacts, which are essential for constructing the LED's electrical and optical components.

💡Photolithography

Photolithography is a process used in semiconductor fabrication to create patterns on a substrate using light-sensitive materials. The script describes it as a key step in forming the fine features of LED chips. It involves coating the LED wafer with a photoresist, exposing it to specific light patterns, and then developing the resist to reveal desired shapes, enabling precise control over the LED structure.

💡Etching

Etching is the process of removing unwanted material from a surface to create a specific shape or pattern. In the context of LED fabrication, etching is used to remove certain parts of the semiconductor layers to define the LED's structure and expose specific layers for electrode placement. The video highlights how different etching methods, such as inductive coupled plasma (ICP) etching, are employed to achieve high precision in LED design.

Highlights

Introduction to Drin Abdullah, a scientist at the Institute of Nano, Opto Electronics Research and Technology at University Science Malaysia, working in optics and photonics with a focus on light-emitting diodes (LEDs).

Explanation of the widespread presence of LEDs in everyday devices such as smartphones, laptops, tablets, smartwatches, cars, and homes, and their importance in modern lighting.

Emphasis on the significant energy consumption of lighting, accounting for about a quarter of the world’s electricity generation.

Overview of various applications of LEDs, including lighting for homes, streets, vehicles, public transport, traffic lights, and even indoor agriculture.

Understanding of LED bulb components, including the diffuser and the yellow-colored phosphor layer which absorbs and emits different colored lights.

Inside an LED bulb, the actual light source is the blue light emitted by the LED, which is then combined with yellow light from the phosphor layer to produce white light.

Two common types of LED packaging: surface-mount device (SMD) LEDs, used in LED bulbs, and dual-in-line (DIL) LEDs, commonly seen in laboratories and electrical shops.

The critical role of the LED chip, a tiny semiconductor, which is the actual source of light in LED bulbs, protected by a polymer dome.

Explanation of LED chip materials: a sapphire substrate, layers of gallium nitride (GaN), and the multiquantum well (MQW) layer, where light is produced through recombination of positive and negative charge carriers.

Tuning the indium composition in MQW layers to produce different light colors, from blue to ultraviolet, making the LED versatile in color emission.

Comparison between LED technology and traditional tungsten lamps, highlighting the inefficiency of tungsten lamps which primarily produce heat energy instead of light.

Detailed fabrication process of LED chips in an advanced lab, starting with the LED epitaxial wafer growth using Metal Organic Chemical Vapor Deposition (MOCVD).

Challenges in the MOCVD process, requiring precise temperature control, monitoring systems, and high-purity precursors to avoid defects in the layers.

Insight into the deposition process of thin layers on the GaN wafer using Electron Beam Evaporator, crucial for constructing the LED chip’s structure.

Explanation of the photolithography process, used to create patterns on the wafer, followed by etching to remove unwanted areas, helping to shape the LED.

Final steps in the LED fabrication process: adding metal electrodes using Electron Beam Evaporator and heating in a furnace to improve conductivity and device performance.

In February 2023, the research team successfully produced one of the world’s most efficient white LEDs, exceeding industry standards with 200 lumens per watt.

Transcripts

and hi everyone my name is drin Abdullah

I a scientist at The Institute of Nano

opto Electronics Research and Technology

uh University Science Malaysia so my my

research is in the field of Optics and

photonics and and one of the most um one

of the photonic device that I'm

interested in is light emitting diodes

or LEDs I'm sure you have heard about

Led before right so you can find LED in

almost everywhere with you now in your

smartphone uh in your laptop your

Smartwatch your tablet and in your car

and and many more nowadays we use light

at home and school pretty much all the

time not just during night and that's

burning a lot of energy if you look at

the all electricity generated when we

talk about the power across the world

then actually about a quarter quarter of

it is used for lighting so that's a huge

fraction of the world and

electricity uh World Electric

electricity generation so a quarter of

the world electricity generation just

goes into lighting up our homes our

streets our schools and all the places

we

go okay these are some of the

application of

LEDs right so the first one is of course

to light up our houses not just during

the night right but also Al during the

day on the top right we have application

in the streets headlamp of your car

public transport traffic light so on and

so forth at the bottom left we use a lot

of energy for for stage lighting for

entertainment for sport and so on and

and more interestingly what we have in

the bottom right we also have used LED

as an artificial sand to grow our

vegetables

indoor right so so that we can have our

garden inside our

home right so we really do need

technologies which can reduce the energy

cost of lighting and that is why light

emitting diodes or LEDs are so

fantastic so what we're going to do in

this talk is to get right inside an LED

bul and find out what is

inside right so this is a fairly typical

LED bul that you might be able to buy in

in any shop in any hardware shop so if

you take this kind of plastic cap off

which is a diffuser it just there to

help spread the lights out and

underneath we find yellow colored Square

components

right each of that square things is an

LED so now we know that led bul contain

multiple LEDs on the printed circuit

board or PCB right so let's focus on one

LED just one of that so the yellow color

is actually made of a material called a

phosphor and what a phosphor does it

absorb light in one color and then REITs

light in another so that's um so that's

not the bit that's not the part that

actually makes

light let us try to remove the yellow

colored layer called phosphor right so

what we can see here now is that inside

the LED bu

we have these bright blue light

emitters so our LEDs in our white light

bulbs are actually giving out blue light

and then when we put the phosphor on top

of it it absorbs some of the blue and

give out yellowish light and the blue

and the yellowish light just now

combined which produce something like uh

something which looks

white right so that's the first thing

that that many white LEDs are actually

giving out blue

light there are few types of package

LEDs these two are the most common one

that we always see we have SMD LEDs or

surface mount device this is the same

type that we saw in LED bul earlier

right and secondly the normal one that

you always see in your school laboratory

or any any electrical shop which is

called double in line or D

LED right so if we zoom in on just one

of

those we've got this chip here with a

sort of polymer Dome over the top of it

to protect it and then contacts going

out to the outside world right so this

very tiny chip is very important it's

actually part which produce light it is

the part that actually produce

light the the package LED can looks

different depending on the packaging

design or the type of application but

the chip is what give out light which is

what we are interested in all right now

let's look at the what this led

structure looks like and what is made

of the part this particular LED design

is a blue LED chip on a patent sire

substrate right so in this chip we have

all classification of solid based on

electrical conductivity which is metal

semiconductor and insulator I'm sure you

have heard you have learned about this

in your school right so we have three

types of or three classification of

solid based on their electrical

conductivity which is metal

semiconductor and insulator and in this

particular chip we have all we use all

types all three types of uh

solid so at the top we have Metals which

are chromium nickel gold and titanium

and gold which act as electrodes for the

charge to flow in inside our chip right

and at the bottom we have a saire layer

which actually act as a substrate for

the whole LED uh chip and if you see in

between um in between the the the safire

and also the metals we have

semiconductor

material right this particular

semiconductor material is a synthetic

and manmade

semiconductor called gallium nitrate it

is not found in

nature and it has been made to give out

blue

light all right so these different

Gallum nitrite layers you can see here

depicted by different colors which are

composed of slightly different from one

with

another they have their specific

function

all right so if you look at here pan pan

is actually a ptype gum nitrate layer

right it is actually just a gallium

nitrate compound with a little bit

magnesium added into it so that it

contains more positive charge carrier

while on the bottom side we have Nan n

type gum nitrite is which is um actually

a Gallum netr layer with silicon added

to it so that it contains more negative

charge carrier so it's opposite to to

the P

again and we've also got uh mqw mq W

layer stand for multiquantum well layer

which act as the location where the

positive and negative charge carrier Rec

combine uh which the process

produce efficiently or the process

efficiently produce

light right right and this particular

mqw layers is what determine the color

of the light that comes out of the

LED and by tuning the indium composition

within the mqw layers we can produce

light uh from from or we can produce

green light we can produce blue light

down to UV ultraviolet uh emission from

that led right we just play around with

the composition of the indium that we we

put in inside the mqw layers all right

the thickness of these layers are as

thin as 3 nanom so it's very very thin

you know 1 nanometer is a billionth of a

meter so therefore only can be seen

using electron microscope and in fact

there are only a few Atomic layers

stick and it is these really tiny layers

of indium gum nitri that actually gives

out

uh the light of our

LED

right when we compare this led to the

old tungsten

lamp right the the the light actually

that comes out from the tungsten lamp is

actually produced by flowing current to

a resistor which is the

tungsten and as the wire becomes so hot

some of the energy is converted into

light as the charge move around in The

Wire so that's why tungsten lamp is very

inefficient very inefficient and it

consume high power because it primarily

produce heat energy as opposed to um

producing

light

right so we have seen the structure of

LED chip right we have seen the

structure of LED chip so now let's look

at the fabrication

process uh we call it process flow that

we use in our Advanced laboratory at IO

so the process begins with LED structure

followed by it deposition meta

photography it etching meta itching and

contact metal deposition and finally we

have this stage called uh and finally

the p and N contact metal deposition to

complete the

process take note that the process flow

is very dependent on the design and the

material of the LED chip that uh that we

have planned to produce okay

let's go through the process one by one

so the first process is Led epital wafer

growth using an equipment called metal

organic chemical vapor deposition or in

short M ocvd right metal organic

chemical vapor

deposition so the schematic on the top

shows uh LED epex structure with many

layers with different colors and at the

bottom we have cake lapis from sarwa

right and both look

very similar right they have layers and

different colors it is because growing

this apeal layer in mocvd is just like

baking a layered cakes in an

oven so we mix our ingredient and we

bake them at a certain temperature to

get a uniform layer on a tray right uh

in osia however in osia however the

ingredient are brought into the reactor

in the form of GES while

uh hitting up the the tray which we call

it substrate in this

process uh into a certain temperature

and by doing that we can produce high

quality gain layers or

we and by doing that high quality G

layers can be grown into a specific

composition and

thicknesses now you might say just bake

it easy but for Kake yeah it is easy but

for epex layer it is very challenging

and very very complex process because of

a number of reasons the first is we need

to use very precise monitoring system to

ensure smooth defect free Gan layers

right that's why the equipment is very

huge secondly we need to precisely

control the the the growing process so

that the thickness can be controlled up

to a nanometer which is just a few atom

stick and

thirdly uh the temperature of the

reactor need to be precisely control as

the growth process is very sensitive

towards a change of temperature even 1°

C right and the fourth is only ultra

high Purity and quality precursors will

be used so that epex wafer will be free

of contamination and defect right

whenever we have contamination and

defect our device our LED will not

perform as um as good as what we want it

to be so if you ask me what are the

types of of gum nitrite that our mvds

can produce so the answer is the

following we can produce gallium nitrite

or Gan we can produce indium gallium

nitrite in Gan aluminium gallium nitrate

right aluminium gum nitrate or Al L Gan

aluminum nitrite aln n type Gan and P

type Gan as what we have uh covered

earlier right so this is a glimpse of

our mocvd operation at I know

so what we do is we load the substrate

into the reactor uh we upload the recipe

that we want and the Machine will do the

baking until our apexi wafer is

ready so we have a fantastic team uh who

are expert in managing and maintaining

this

equipment so in um in February 2023 we

managed to produce one of the most

efficient white LED in the world

exceeding industry standard at uh 200

Lum for uh 200 Lumen per what

right all right so that is the first

step which is producing LED epex using

mocvd then we move to our fabrication

lab where the subsequent processes will

be performed

here well before we go to the next

process in fabrication

LEDs um uh let's familiarize with some

processes that we do here the first is

process called deposition right what is

deposition deposition I is the process

of adding thin layer of material on top

of our gum nitr layer so we use

equipment called e beam Electron Beam

evaporator deposition to do it right and

the second process is photo lithography

process so photography process is a

process of using light to create

specific pattern on the layer using

light sensitive polymer or we we or

using light sensitive polymer uh which

we call it um photo resist right the

third process that you need to

familiarize is uh etching process so

etching process is a process of removing

a part or area on our epex wafer to form

a desired shape using uh

gases okay now let's go to the next

stage which is it

deposition in this stage we deposit

indium oxide layer on top of our LED

wafer with a thickness around 110

nanomer do you still remember the name

of equipment that we used to deposit

I yes it is a Electron Beam evaporator

right then the next stage is to create a

Mesa or top head structure on our sample

using photography process this is done

inside a a room that only have yellow

light and the reason is because the

writing process using light is very

sensitive towards blue and UV

light and we use equipment called musers

liography to do the

writing after the process this is how

our sample will look

like right so we have now added a

pattern using a uh photo resist or PR

layer right so the next stage is it

etching process we

use equipment called inductive couple

plasma reactive ion etching or I

ICP uh and and some part of the I will

be removed out leaving just the pr

pattern that we have transferred in the

uh photoi photography process earlier

then we will remove the pr layer photo

resist layer and continue to as the AP

wafer until the endan

layer right and the reason of doing this

is to expose the engan layer so that we

can create an electrod on top of it

right so that we can create an electrode

electrode uh on top of it remember our

LED should have two electrodes one is

positive which is connected to a p Gan

layer to the top p g layer and another

one is is is a negative electrode which

is connected to n g

layer now our LED begins to take shape

right but we are not finished we still

need to add the electrodes which made of

metal right and we do that by doing end

contact deposition again using eim

evaporator but since we only want to

deposit the metal which is titanium Orum

or titanium gold at the end layer only

therefore we need to use photography

again to do

so so the last stage is we need to add

another metal deposition for creating

another layer on both negative and

positive electrodes which we also need

to perform using um ebm evaporator

together with photography process to

expose the position only at the area

that we want this time the electrode is

composed of chromium nickel and

gold so actually we have another step

right after we have completed n and p

metal deposition right um metal contact

deposition and the process is called

metalization so what we do we hit up the

deposited metal contact using equipment

either rapid thermal processing or RTP

or furnace all right until a certain

temperature the difference between these

two equipment is RTP provide quick um

heating while furnace provide more

slower but controll heating on our

sample right you might ask me why we

want to heat up the the sample why we

want to heat up the deposited metal

contact the reason is two we have two

reasons the first is we want to improve

their electrical conductivity to ensure

strong and stable omic

contact secondly this process is very

crucial in enhancing the interface

quality between the metal and

semiconductor layer right so we have

layers of semiconductor but on top of it

we have this very

small uh patch of metal layer of metal

right so therefore we we we want we need

to increase the the interface quality

between these two different type of

material so by doing that we can reduce

contact resistance and improving overall

device performance and

reliability all right so with that we

finally have our blue LED chip that will

if efficiently light up whenever we

apply voltage um between the two metal

contacts right as you can see from the

left figure here this is again the

cross-section of LED chip based on the

process that we have covered earlier and

and another figure shows um the top view

of the LED chip that we have produced in

the fabrication process all right so I

hope that you all learned something

during this um session and thank you for

your attention and I wish you all the

best for your future thank you