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SCHOOL OF ELECTRICAL AND ELECTRONIC

ENGINEERING

Progress Report

Temperature dependent characteristics of IGZO SBTFTs

Yuxin Ji

8573039

Supervised by:

Prof. Aimin Song

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Nomenclature *All notations used in this report are listed here. Explanations of notations following each formula are thus omitted.

Abbreviation Quantity Magnitude/Unit

Cc Depletion layer capacitance F

Cox Gate-oxide capacitance F

Ea Activation energy eV

EF Fermi Level eV

Eg Bandgap eV

ε0 Electric constant 8.854x10-12 F/m

F Electric field strength N/C

h Planck’s constant 4.136x10-15

ħ Reduced Planck’s constant h/2π

IDS Drain source current A

IDSO Prefactor of drain current /

J Current density A/m2

k Boltzmann Constant 1.3806 × 10-23 m2 kg s-2 K-1

L Gate Length m

m* Effective mass (of a carrier) 9.11×10−31 kg

N Dopant concentration m-3

q Elementary charge 1.602x10-19 C

S Surface area m2

T Temperature K

VTH Threshold voltage V

Vs-th Subthreshold swing V

VDS Drain source voltage V

VGS Gate source voltage V

Von Turn-on voltage V

W Gate width m

X Electron affinity V

μ Carrier mobility m2/Vs

μeff Effective mobility m2/Vs

σ Conductivity S/m

Φ Work function V

ΦB Schottky barrier V

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Table of Contents

Nomenclature ....................................................................................................... 2

1. Background ....................................................................................................... 4

1.1 Aims ............................................................................................................................................. 4

1.2 Objectives .................................................................................................................................... 4

1.3 Motivation ................................................................................................................................... 4

1.3.1 a-IGZO and Flat-panel Display ................................................................................................. 4

1.3.2 SBTFT and Temperature.......................................................................................................... 5

1.4 Literature Review ......................................................................................................................... 5

2. Progress to Date ................................................................................................ 5

2.1 Project Plan .................................................................................................................................. 5

2.2 Health and Safety Risk Assessment ............................................................................................... 6

2.3 Technical Risk Analysis.................................................................................................................. 6

2.4 Practical Progress ......................................................................................................................... 6

2.4.1 The Discovery of a-IGZO ......................................................................................................... 6

2.4.2 Characteristics of a-IGZO ........................................................................................................ 7

2.4.3 TFT......................................................................................................................................... 9

2.4.4 Metal-Semiconductor Junction ..............................................................................................11

References .......................................................................................................... 14

Appendices ......................................................................................................... 16

1. Gantt Chart of Project Plans ...........................................................................................................16

2. Health and Safety Risk Assessment ................................................................................................17

3. Technical Risk Analysis...................................................................................................................20

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1. Background

1.1 Aims

The aim of this project is to investigate characteristics of an amorphous Indium-Gallium-Zinc-Oxide

Schottky Barrier Thin-Film Transistor (a-IGZO SBTFT) which particularly relate to and vary with

temperature alterations by inspecting and revealing the temperature dependence of properties of

a-IGZO SBTFTs via a series of measurements and analysis.

1.2 Objectives

There are a series of tasks that need to be undertaken in order to fully understand the effects of

temperature on the performance of a SBTFT. These include:

Intensive literature review on relevant key concepts

Simulated calculation on the output and transfer characteristics of a SBTFT

Technical risk assessment and familiarization of equipment Experiment design on

Determination of Schottky barrier height

Measurement of IDS with varying temperature (T-1/T-(1/4))

Measurement of IDS vs. VGS and IDS vs. VDS

Analysis of data collected from the experiments, especially on Dominance of different conduction mechanisms

Determination of transfer and output characteristics

Effects of varying temperature on IDS and thus the performance

1.3 Motivation

1.3.1 a-IGZO and Flat-panel Display

The 21st century has witnessed an increasingly prosperous paperless media, and consequently the

demand for flat-panel display has been augmenting in recent years. Transparent electronic

components therefore come to the fore in the research field. With a wide bandgap and an oxide

channel which is able to function as both an active and a passive element, TFT is anticipated as one

of the most auspicious material for future generation flat-panel display. Here, what really makes TFT

excel in such applications is the composition of the oxide layer (Fortunato, Barquinha and Martins,

2012).

The oxide active layer discussed in this report is composed of a-IGZO which has been intensively

investigated, as it exhibits a higher mobility (10~25cm2/Vs) compared to that of hydrogenated

amorphous silicon (0.1~0.5cm2/Vs) and can be fabricated under low temperature (200°C). Hence, a-

IGZO TFT appears to be an extraordinarily suitable material to construct active matrix display panels

on plastic substrates with large size, high resolution and low power consumption (Fortunato,

Barquinha and Martins, 2012).

So far, there are many successful commercial digital devices whose display panels are made of IGZO

TFTs. Sharp Electronics started to mass-produce IGZO TFT LCD panels and introduced the panels in

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smartphones, tablets and TVs (Androidauthority, 2014). iPad Air, which was announced by Apple in

2013, received an overwhelming welcome in the market (extremetech.com, 2013). Overall, statistics

from the consumer’s market prove that IGZO TFT will be a mainstream constructing material for

matrix display in the near future. Therefore, its novel characteristics and commercial value are the

first motivation of this project.

1.3.2 SBTFT and Temperature

The Schottky barrier (SB), formed from deformation of energy bands in the metal-semiconductor

interface, is a unique rectifying property that is put to good use in many electronic devices such as

Schottky diode and Schottky transistor. These devices work differently from conventional PN-

junction based devices in carrier transport mechanisms, fabrication, application and many other

aspects (Chandra and Prasad, 1983).

Till now, researchers have reported very few works on SBTFTs, let alone SBTFTs with a-IGZO active

channel. One possible reason for this is that grain boundaries present in the channel may deteriorate

junction characteristics, which consequently results in devices with intolerable performance (Lin et al., 2001). Therefore, the second motivation of the project is to investigate the characteristics of a -

IGZO SBTFT, a relatively new device, so as to replace state-of-the-art SB poly-Si TFT for an even better

performance.

1.4 Literature Review

In this section, reviewed literatures are categorized here in accordance with the key questions

discussed in each weekly meeting. These categories are listed as follows.

The chemical structure of IGZO

Composition and fabrication of a TFT

Mobility and factors that determine the mobility of IGZO

Main conduction mechanisms of IGZO

Conduction mechanism dominance under different conditions

The concept of threshold voltage, turn-on voltage and subthreshold swing

Transfer and output characteristics of TFT

The concept of Schottky barrier

The concept of thermionic emission and Schottky effect

I-V characteristic of a Schottky diode

Since literature review is of paramount importance in earlier stages of the project, time and effort

allocated to the project was devoted entirely to literature review until Week 6, and will be

continuously allotted to more intensive literature review process in the following weeks for a higher

level of solidity and profundity in understanding relevant concepts. Therefore, a detailed elaboration

of findings from literature review will be discussed in Section 2.4.

2. Progress to Date

2.1 Project Plan

This project is a research-based project which requires intensive research and literature review

processes at preparation stage, which will last for around 9 to 12 weeks. Amongst the 12 weeks, 2

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weeks will be spent on generating a progress report, illustrating the progress up to Week 6. In the

rest of the weeks, students undertaking the project are given specific questions to do research on,

and are expected to present their answers to the group members and the supervisor during weekly

meetings in a logical manner.

The next stage is experimental stage, which will be started with technical risk assessment and hands-

on familiarization of equipment. Lasting for about 2 weeks, this procedure is crucial because the

experiments will be conducted in D13a/b laboratory/cleanroom specifically designed for

microelectronics and nanostructures, which will be a relatively unfamiliar experience. From February

2016 onwards, 3 to 4 afternoons will be spent to perform a series of experiments so as to gather

data for relevant analysis later. The rest of the time of Semester 2 will be used to generate a final

report and prepare for the oral examination afterwards. If there are abundant time left, fabrication

of new devices can be considered as an optional exploration of the topic.

A detailed Gantt Chart of the project plan is provided in Appendices 1. Note that this project plan is

not finalized and always subject to change.

2.2 Health and Safety Risk Assessment

Please refer to Appendices 2.

2.3 Technical Risk Analysis

Please refer to Appendices 3.

2.4 Practical Progress

Following Section 1.4, this section is aimed at elaborating and corroborating relevant theories and

findings from various literatures.

2.4.1 The Discovery of a-IGZO

The discovery of a-IGZO started and advanced with commercial flat-panel display industry. In days

of yore, the semiconductors inside display medium were fabricated using traditionally accepted

channel materials such as Si, GaAs and GaN. In late 1990s, novel and unconventional metal oxide

such as ZnO was then well recognized as a better substitute due to its extraordinary intrinsic

properties at heterojuctions. More importantly, polycrystalline ZnO (poly-ZnO) still possesses its

active characteristics when the device is fabricated below 300°C, making it a more promising channel

layer than hydrogenated amorphous silicon (a-Si:H) which was previously prevailing in all flat-panel

displays (Kamiya, Nomura and Hosono, 2010).

Since 2000 onwards, there has been an increasingly research interest in flexible electronics, and

more characteristics of ZnO was revealed at that time. What makes ZnO desirable is the remarkable

low fabrication temperature below 300°C, but it suffers from instability and unrilability brought by

grain boundaries. Even worse, threshold voltage of TFT fabricated using poly-ZnO cannot be

managed easily because of a great amount of residual free electrons (>1017 cm−3) in its native defects

(Kamiya, Nomura and Hosono, 2010).

In order to avoid these disadvantages, researchers started to fabricate TFTs with single-crystalline

InGaZnO4 whose residual carrier density was lower. Accidentally, it was discovered that amorphous

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IGZO compound had even lower residual carrier density (<1015 cm−3). What is more plausible is that

grain boundary problems rarely exist in a-IGZO, thus making it a more promising channel material

for the next generation TFTs. Therefore, as a natural progression, the first a-IGZO TFT was reported

in 2004 (Kamiya, Nomura and Hosono, 2010).

2.4.2 Characteristics of a-IGZO

2.4.2.1 Bandgap and Transparency

A-IGZO is desirable for flexible electronics for a lot of reasons, and one of them is its transparency

under visible light. On deciding whether a material is transparent, there are a great number of factors

that should be taken into account holistically because the process of penetration of photons through

the material is fairly complicated. However, one of the dominant factors among them is the size of

the bandgap. Once photons possess enough energy to excite electrons across the bandgap, the

photons will be absorbed when travelling through the material. On the contrary, any photons which

are unable to provide energy more than the bandgap of the material will penetrate (or be scattered

in some cases) the material, and this is when a material becomes transparent.

The wavelength of visible light ranges from 400nm to 700nm. According to E =ℎ𝑐

𝜆, 400nm will result

in an energy level of 3eV, which means any material with a bandgap wider than 3eV will be

transparent. Hence, a-IGZO’s 3.4eV bandgap accounts for its transparency.

Wide bandgap, though desirable, brings about another problem, which is a low carrier density and

thus mobility because electrons will be less likely to be excited onto conduction band once they need

more energy to cross the bandgap. One practical solution is doping a-IGZO with Heavy Post

Transition Metal (HPTM) cations, which gives rise to a higher concentration of electrons (Chen et al.,

2009). With the majority carrier being electrons, a-IGZO becomes an n-type extrinsic semiconductor.

2.4.2.2 Mobility

When electric field is applied, electrons will first be accelerated by the electrostatic force, and then

eventually reach a relatively constant velocity, Vd, which is named as drift velocity. Mobility (𝜇), a

quantity used to describe how fast an electron (or a carrier in a broad sense) moves, is defined as

the ratio of drift velocity to the applied field. Scattering, namely the bombardment between

electrons and other particles, affects mobility to a large extent. The relationship is as follows

μ =𝑞

𝑚∗𝜏 (1)

Where 𝜏 represents momentum relaxation time, defined as how long the carrier is accelerated by

the electric filed until it is scattered and thus its original momentum is lost. Two types of scattering

are dominant interfering factors: ionized impurity scattering which is from doping impurity carriers,

and phonon scattering which is from the vibration of atoms of the material. The former is closely

related to doping concentration, and the latter is decided by temperature (Ferry, 2000).

Mobility is a vital concept because it can directly affect the conductivity of the semiconductor, with

a relationship given by:

𝜎 = 𝜇𝑞𝑁 (2)

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A-IGZO is a more preferable amorphous material than a-Si due to its better mobility (10~25 cm2/Vs

vs. 0.1~0.5cm2/Vs). This can be explained from their respective microscopic structure (Figure 1).

IGZO is composed of isotropic cation 5s-orbitals which still maintain a great amount of overlap when

its structure becomes amorphous, while a-Si is composed of anisotropic Si sp3-orbitals which makes

sufficient amount of overlap of orbitals unlikely.

Figure 1: orbital overlap of IGZO and Si (crystalline and amorphous) (Chen et al., 2009)

2.4.2.3 Structure

The structure of IGZO is rhombohedrally symmetrical. It is a special type of stratified structure with

alternating laminated layers of InO2- and GaO(ZnO)+.

Within the structure, ZnO is responsible for carrier concentration due to its intrinsic properties

explained in Section 2.4.1. InO is the conduction path responsible for carrier transport owing to its

high mobility and carrier concentration. InO also alleviates native traps present inside the structure.

GaO, with a stronger bonding than either ZnO or InO and a low melting point, forms the amorphous

structure of IGZO.

2.4.2.4 Conduction Mechanism in IGZO

There are many different models on how carriers are transported in IGZO. In this report, the

mechanisms discussed will be confined to 2 models: band conduction and hopping conduction.

2.4.2.4.1 Band Conduction

Band conduction refers to the conduction of carriers in the free delocal ized states beyond bandgaps.

Such conduction mechanism can be described using Arrhenius Equation:

𝐼𝐷𝑆 = 𝐼𝐷𝑆𝑂 × 𝑒−𝐸𝑎𝐾𝑇 (3)

Rearranging, the equation becomes:

𝑙𝑛𝐼𝐷𝑆 =−𝐸𝑎

𝐾×

1

𝑇+ 𝑙𝑛𝐼𝐷𝑆𝑂 (4)

A linear correlation between InIDS and T-1 can be observed. Such correlation can be a strong indicator

of band conduction dominant circumstances. In Figure 2(a), a perfectly linear relationship between

InIDS and T-1 can be observed from 300K to 80K, implying that band conduction is dominant within

this temperature range.

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Figure 2: graph of InIDS vs. T-1 and graph of InIDS vs. T-1/4 (Hossain Chowdhury, Migliorato and Jang, 2013)

2.4.2.4.2 Hopping Conduction

Hopping conduction refers to the conduction of carriers around localized states around Fermi level. There are basically two types of hopping: Nearest neighbor hopping and variable range hopping

(VRH). The latter is more frequent and dominant (McClintock, Meredith and Wigmore, 1984).

VRH can be described using Mott’s Equation:

𝐼𝐷𝑆 = 𝐼𝐷𝑆𝑂 × 𝑒−𝐵

𝑇1/4 (5)

Rearranging, the equation becomes:

𝑙𝑛𝐼𝐷𝑆 = 𝐵 ×1

𝑇14

+ 𝑙𝑛𝐼𝐷𝑆𝑂 (6)

A linear correlation between InIDS and T-1/4 can be observed. Such correlation can be a strong

indicator of VRH dominant circumstances. In Figure 2(b), a linear relationship between InIDS and T-

1/4 can be observed from 80K below, implying that VRH is dominant within this temperature range.

Another classic conduction model called percolation also claims a linear relationship between InIDS

and T-1/4, although the correlation is weaker. It also claims that as a-IGZO is amorphous, VRH is a less

likely transport mechanism than percolation. However, this is still an active area of debate, so no

decisive conclusion can be made till now.

2.4.3 TFT

2.4.3.1 Composition

TFT, the core device of transparent electronics, consists of 4 components: substrate, semiconductor

channel, gate insulator and electrodes (named as source and drain).

Gate insulator is made of dielectric materials. Usually dielectrics with high electric constant are

preferred because they are effective in reducing operational voltage, threshold voltage and gate

leakage currents. However, a rise in electric constant would reduce bandgap, and thus decrease

conduction band offset energy. This results in charge injection and trapping which is the origin of

electrical instability of TFTs, and noise is one form of such instability. Special dielectric structure is

helpful to reduce noise. For instance, in 2012, an HfO2/SiO2 bilayer dielectric is reported with Hooge’s

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parameters of 2x10-3, which is one order of magnitude lower than that of a single layered dielectric

(Su et al., 2012).

Electrodes, made from metals, contact with the semiconductor active channel, forming a metal-

semiconductor junction where a Schottky Barrier is generated from the deformation of energy bands.

This will be discussed in further details in Section 2.4.4.

2.4.3.2 Ideal Behavior of a TFT

2.4.3.2.1 Output Characteristics

When a TFT is working, source is grounded while a positive voltage is applied to the drain. Two

circumstances should be considered when discussing the behavior of a TFT. Figure 3 illustrates these

circumstances in details.

Figure 3: three circumstances under which a TFT works (Wager, Keszler and Presley, 2008)

1) If gate voltage, VGS, is less than the turn-on voltage, Von (the minimum voltage needed to turn on

the TFT), no drain current, IDS, exists, because there is no accumulation of electrons at channel-gate

interface.

2) If VGS>Von, electrons are introduced from the source to the channel to form an accumulation layer,

and extra electrons will travel through this layer and eventually be withdrawn at drain.

a) Now if VDS<<VGS-Von, where VDS represents drain-source voltage, the behavior obeys Ohm’s

Law. Namely,𝐼𝐷𝑆 =𝑉𝐷𝑆

𝑅𝑐 where Rc is the resistance of the channel.

b) If VGS is no longer negligible compared to VGS-Von, the behavior is now sublinear and finally

reaches a saturation at VDS=VGS-Von.

2.4.3.2.2 Transfer Characteristics

TFT possesses a threshold voltage, VTH, which is defined as the minimum level that VGS should reach

to push Fermi level to the conduction band. Subsequently, the amount of VGS required to change IDS

by a decade, is named as subthreshold swing, Vs-th. Vs-th can be calculated as follows:

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𝑉𝑠−𝑡ℎ = ln(10)𝑘𝑇

𝑞(1 +

𝐶𝑑

𝐶𝑜𝑥) (7)

, where 𝐶𝑑 is depletion layer capacitance and 𝐶𝑜𝑥 is the gate-oxide capacitance. Vs-th is inevitable

due to the fact that originally no conduction path subsists in the channel. Therefore, there is a

minimum level that VGS should reach in order to form a depletion layer inside the channel. By

substituting T=300K into the Equation, the minimum swing at room temperature is obtained, which

is around 60mV/dec.

Figure 4 shows the transfer characteristic curve on both linear and log scales.

Figure 4: transfer characteristics of a TFT on a linear and log scale (Fortunato, Barquinha and Martins, 2012)

The on-off ratio is the ratio of maximum IDS to the minimum IDS. A large on-off ratio is desirable

especially when the TFT is used in a high frequency design.

On log scale, it can be observed that IDS only starts to vary normally when VGS reaches Von as

described earlier in this section. As VGS increases, IDS increases linearly in the subthreshold region.

However, mobility of electrons will eventually rise to its limits, and this accounts for the saturation

region of the curve. On linear scale, the curve is almost linear. By extrapolating the line backwards,

the value of VTH can be obtained. In this curve, IDS can be calculated as follows:

𝐼𝐷𝑆 = 𝜇𝑒𝑓𝑓𝐶𝑜𝑥𝑊

𝐿((𝑉𝐺𝑆 − 𝑉𝑇𝐻 )𝑉𝐷𝑆 −

𝑉𝐷𝑆2

2) (8)

2.4.4 Metal-Semiconductor Junction

2.4.4.1 Schottky Barrier

A metal-semiconductor junction is formed when a semiconductor and a metal are put to close

contact, and is the most primitive semiconducting device. Such junction can be either rectifying or

non-rectifying, depending on a decisive factor called Schottky barrier.

The material (metal or semiconductor) with a higher Fermi level, EF, will have a higher carrier

concentration compared to that with a lower EF. Therefore, when they are brought into close contact,

carriers will flow from a higher concentration region to a lower concentration region. Consequently,

major carriers in the material whose carrier concentration is low will be pushed uphill, leading to a

deformation of energy band. This process will eventually stop when EF of two materials are in

equilibrium.

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As a result, two distinctive features take shape. Firstly, the deformation of energy band creates a

band barrier and this is the Schottky barrier, ΦB. Secondly, there will be a depletion layer adjacent

to the barrier, and this region is devoid of any carrier because carrier equilibrium is already reached.

Figure 5 shows the deformation of energy bands for both n-type and p-type semiconductors.

Figure 5: deformation of energy bands for both n-type and p-type semiconductors (Warwick University, 2015)

The magnitude of Schottky barrier is called Schottky barrier height. The relationship of Schottky barrier height and bandgap (Eg) can be expressed as follows:

q𝛷𝐵𝑛+q𝛷𝐵𝑝=𝐸𝑔 (9)

Figuring out qΦB for any specific material has been a baffling topic for decades. Many researchers have been trying to construct models to describe qΦB. One of the most primitive model is Schottky-

Mott Model, which states that qΦB for an n-type semiconductor equals to the work function of the

metal minus its electron affinity. Its mathematical expression is:

q𝛷𝐵𝑛 = qΦM − qX (10)

With Equation (9), qΦB for the p-type doping of the same semiconductor can be obtained.

q𝛷𝐵𝑝 = 𝐸𝑔 − q𝛷𝐵𝑛=𝐸𝑔 − (qΦM − qX) = 𝐸𝑔 − qΦM + qX (11)

Despite its intuitiveness, this model was proved to be less useful than expected when real -world

measurements were performed. Although the Model suggests that with a higher work function of

the metal comes a higher barrier height, which is true, the work function dependence of barrier

height is far weaker as observed in practical experiments. In Figure 6, it is obvious that work function-

barrier height relationship of different metal-semiconductor combination does not at all fit the

theoretical prediction. That is why more and more advanced theoretical models appear to provide

a more accurate prediction of barrier height.

Figure 6: graph of Schottky barrier height vs. metal work function (Tung, 2014)

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2.4.4.2 Thermionic Emission

Thermionic emission occurs when carriers inside a material, after receiving thermal energy greater

than its work function, are emitted to the vacuum or to overcome a potential barrier. Current density

of such emission can be expressed using Richardson Equation:

𝐽 = 𝐴𝑇 2𝑒−𝑞Φ

𝐾𝑇 (12)

Thermionic emission is the main transport mechanism across a metal-semiconductor interface.

Together with the rectifying property of a metal-semiconductor junction, thermionic emission can

be put to good use in the form of a diode. Such diode is called Schottky Diode.

2.4.4.3 Schottky Diode

Schottky diode is basically constructed using closely contacted metal and semiconductor. The

working principle is just based on the rectifying behavior of a metal-semiconductor junction. Figure

7 shows the structure of a Schottky diode.

Figure 7: structure of a Schottky diode (Fonstad, 2003)

The output characteristics of a Schottky diode is very much similar to a PN diode, with a smaller Von

(0.15~0.45V compared to 0.7V in PN diode) and a steeper IV curve. One significant difference is that

the recovery time of a Schottky diode is virtually non-existent because there is nothing to recover

due to the presence of the depletion layer near the barrier. Compared to a PN diode (whose recovery

time is 100ns at best), Schottky diode is an ideal device for high frequency switches.

As the main transport mechanism of a Schottky Diode is thermionic emission, Equation (12) can be

applied to derive the current flowing through the diode.

𝐼𝑡𝑜𝑡𝑎𝑙 = 𝐼𝑚𝑠 − 𝐼𝑠𝑚 = 𝐽𝑚𝑠 × 𝑆 − 𝐽𝑠𝑚 × 𝑆 (13)

Therefore

𝐼𝑡𝑜𝑡𝑎𝑙 = 𝑆 × 𝐴𝑇2 × 𝑒−(Φ𝐵 −𝑞𝑉)

𝐾𝑇 − 𝑆 × 𝐴𝑇2 × 𝑒−Φ𝐵𝐾𝑇

𝐼𝑡𝑜𝑡𝑎𝑙 = 𝐼𝑠𝑚 × (𝑒𝑞𝑉

𝐾𝑇 − 1) (14)

Where S is the area of the interface

2.4.4.4 Schottky Effect

When a Schottky diode is biased, an electric field of magnitude F is created. This field will lower the

Schottky barrier and thus further increase the emission current. This is a field-enhanced thermionic

emission, which is called Schottky Effect. Thus, Equation (12) can be modified as follows:

𝐽 = 𝐴𝑇2𝑒−𝑞(Φ𝐵−ΔW)

𝐾𝑇 and ΔW = √𝑒3 𝐹

4𝜋𝜀0 (15)

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Low-Frequent Noise and the Enhancement of a-IGZO TFT Electrical Performance. JOURNAL OF DISPLAY

TECHNOLOGY, 8(12), pp.695-698.

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http://academic.brooklyn.cuny.edu/physics/tung/Schottky/SiSBH1.jpg [Accessed 6 Nov. 2015].

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Appendices

1. Gantt Chart of Project Plans

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2. Health and Safety Risk Assessment

2.1 General Safety Guidance for Users of D13a/b Laboratory and Cleanroom

18

2.2 Risk Assessment Pro-forma

19

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3. Technical Risk Analysis

Until Week 6, the project has not involved any practical work, and this situation may continue for

the rest of the Semester 1. In addition, there will be an exclusive session for technical risk assessment

in Semester 2. Therefore, this part is deliberately omitted and will be presented in a well -rounded

manner in the Final Report.