Selective etching of InP in InAs/InP nanowires resulting in 11 nm nanogaps

1Institut für Halbleitertechnik, Technische Universität Braunschweig, Germany; 2Solid State Physics / The Nanometer Structure Consortium, Lund University, Sweden; 3Helmholtz-Zentrum für Energie und Materialien, Berlin, Germany; 4Physikalisch-Technische Bundesanstalt, Braunschweig, Germany; 5Department of Molecular Electronics, TU München, Germany; 6Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin, Germany

Muhammed Ihab Schukfeh1,6; Kristian Storm2; Kimberly Dick Thelander2; Nelia Wanderka3; Peter Hinze4; Allan Hansen1; Claes Thelander2; Thomas Weimann4; Lars Samuelson1 and Marc Tornow1,5

Motivation

• Nanogap electrodes received a lot of attention in recent years• Applications range from sensing to molecular – and bioelectronics• Status quo: in most cases at least one electrode is made of metal

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 2 of 10

Motivation

• Nanogap electrodes received a lot of attention in recent years• Applications range from sensing to molecular – and bioelectronics• Status quo: in most cases at least one electrode is made of metal

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 2 of 10

Motivation

• Nanogap electrodes received a lot of attention in recent years• Applications range from sensing to molecular – and bioelectronics• Status quo: in most cases at least one electrode is made of metal

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 2 of 10

Motivation

• Nanogap electrodes received a lot of attention in recent years• Applications range from sensing to molecular – and bioelectronics• Status quo: in most cases at least one electrode is made of metal

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 2 of 10

Motivation

• Nanogap electrodes received a lot of attention in recent years• Applications range from sensing to molecular – and bioelectronics• Status quo: in most cases at least one electrode is made of metal

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 2 of 10

Motivation

• Nanogap electrodes received a lot of attention in recent years• Applications range from sensing to molecular – and bioelectronics• Status quo: in most cases at least one electrode is made of metal

Advantages of semiconducting electrodes:• Tailoring physical and electrical properties according to desired application:

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 2 of 10

Motivation

• Nanogap electrodes received a lot of attention in recent years• Applications range from sensing to molecular – and bioelectronics• Status quo: in most cases at least one electrode is made of metal

Advantages of semiconducting electrodes:• Tailoring physical and electrical properties according to desired application:

• Doping type

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 2 of 10

Motivation

• Nanogap electrodes received a lot of attention in recent years• Applications range from sensing to molecular – and bioelectronics• Status quo: in most cases at least one electrode is made of metal

Advantages of semiconducting electrodes:• Tailoring physical and electrical properties according to desired application:

• Doping type• Doping concentration

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 2 of 10

Motivation

• Nanogap electrodes received a lot of attention in recent years• Applications range from sensing to molecular – and bioelectronics• Status quo: in most cases at least one electrode is made of metal

Advantages of semiconducting electrodes:• Tailoring physical and electrical properties according to desired application:

• Doping type• Doping concentration• Band gap

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 2 of 10

Motivation

• Nanogap electrodes received a lot of attention in recent years• Applications range from sensing to molecular – and bioelectronics• Status quo: in most cases at least one electrode is made of metal

Advantages of semiconducting electrodes:• Tailoring physical and electrical properties according to desired application:

• Doping type• Doping concentration• Band gap• Availability of native oxide

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 2 of 10

Motivation

• Nanogap electrodes received a lot of attention in recent years• Applications range from sensing to molecular – and bioelectronics• Status quo: in most cases at least one electrode is made of metal

Advantages of semiconducting electrodes:• Tailoring physical and electrical properties according to desired application:

• Doping type• Doping concentration• Band gap• Availability of native oxide

Challenges for semiconducting nanogap electrodes:

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 2 of 10

Motivation

• Nanogap electrodes received a lot of attention in recent years• Applications range from sensing to molecular – and bioelectronics• Status quo: in most cases at least one electrode is made of metal

Advantages of semiconducting electrodes:• Tailoring physical and electrical properties according to desired application:

• Doping type• Doping concentration• Band gap• Availability of native oxide

Challenges for semiconducting nanogap electrodes:• Technologically more demanding than metal nanogaps

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 2 of 10

Motivation

• Nanogap electrodes received a lot of attention in recent years• Applications range from sensing to molecular – and bioelectronics• Status quo: in most cases at least one electrode is made of metal

Advantages of semiconducting electrodes:• Tailoring physical and electrical properties according to desired application:

• Doping type• Doping concentration• Band gap• Availability of native oxide

Challenges for semiconducting nanogap electrodes:• Technologically more demanding than metal nanogaps• Implementation of a gate

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 2 of 10

Our approach:• Template-based, removing a sacrificial layer

Technological Approach

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 3 of 10

Our approach:• Template-based, removing a sacrificial layer• Material system of choice: InAs nanowires with embedded InP segments

Technological Approach

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 3 of 10

Our approach:• Template-based, removing a sacrificial layer• Material system of choice: InAs nanowires with embedded InP segments

Technological Approach

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 3 of 10

M.I Schukfeh et al., Nanotechnology 25 (46), 2014

Our approach:• Template-based, removing a sacrificial layer• Material system of choice: InAs nanowires with embedded InP segments

Technological Approach

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 3 of 10

InAs InAs

InP 10 - 60 nm

Our approach:• Template-based, removing a sacrificial layer• Material system of choice: InAs nanowires with embedded InP segments

Technological Approach

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 3 of 10

InAs InAs

InP 10 - 60 nm

+ selective InP etching

Our approach:• Template-based, removing a sacrificial layer• Material system of choice: InAs nanowires with embedded InP segments

Technological Approach

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 3 of 10

InAsInAs

gap10 - 60 nm

Our approach:• Template-based, removing a sacrificial layer• Material system of choice: InAs nanowires with embedded InP segments

Advantages:• InP-segments can be grown in any thickness d > 5 nm

Technological Approach

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 3 of 10

InAsInAs

gap10 - 60 nm

Our approach:• Template-based, removing a sacrificial layer• Material system of choice: InAs nanowires with embedded InP segments

Advantages:• InP-segments can be grown in any thickness d > 5 nm

• Nanowires are transferred onto Si / SiO2 substrates backgate available

Technological Approach

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 3 of 10

InAsInAs

gap10 - 60 nm

Our approach:• Template-based, removing a sacrificial layer• Material system of choice: InAs nanowires with embedded InP segments

Advantages:• InP-segments can be grown in any thickness d > 5 nm

• Nanowires are transferred onto Si / SiO2 substrates backgate available

• Resulting nanoelectrodes: InAs Fermi level pinning above conduction band edge at surface

Technological Approach

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 3 of 10

InAsInAs

gap10 - 60 nm

Hydrobromic acid (HBr) is known to etch macroscopic InP

Selective wet etching of InP nanosegments

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 4 of 10

Hydrobromic acid (HBr) is known to etch macroscopic InP• Macroscopic recipes cannot simply be converted to the nanoscale

Selective wet etching of InP nanosegments

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 4 of 10

Hydrobromic acid (HBr) is known to etch macroscopic InP• Macroscopic recipes cannot simply be converted to the nanoscale

Novel etching method based on HBr

Selective wet etching of InP nanosegments

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 4 of 10

Hydrobromic acid (HBr) is known to etch macroscopic InP• Macroscopic recipes cannot simply be converted to the nanoscale

Novel etching method based on HBr• HBr in water is a strong acid (strongly ionized) high HBr

concentrations necessary

Selective wet etching of InP nanosegments

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 4 of 10

Hydrobromic acid (HBr) is known to etch macroscopic InP• Macroscopic recipes cannot simply be converted to the nanoscale

Novel etching method based on HBr• HBr in water is a strong acid (strongly ionized) high HBr

concentrations necessary• HBr in acetic acid (HAc) is a weak acid (weakly ionized) lower

concentration of HBr sufficient

Selective wet etching of InP nanosegments

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 4 of 10

HAc:HBr solutions with variables: HBr concentration, etching time and illumination

Etching recipes

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 5 of 10

HAc:HBr solutions with variables: HBr concentration, etching time and illumination

Etching recipes

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 5 of 10

HAc (ml) HBr (ml) Time (min) Illumination

Recipe A 13 7 2:30 no

HAc:HBr solutions with variables: HBr concentration, etching time and illumination

Etching recipes

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 5 of 10

HAc (ml) HBr (ml) Time (min) Illumination

Recipe A 13 7 2:30 no

Recipe B 17 3 2:30 no

HAc:HBr solutions with variables: HBr concentration, etching time and illumination

Etching recipes

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 5 of 10

HAc (ml) HBr (ml) Time (min) Illumination

Recipe A 13 7 2:30 no

Recipe B 17 3 2:30 no

Recipe C 17 3 2:30 yes

HAc:HBr solutions with variables: HBr concentration, etching time and illumination

Etching recipes

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 5 of 10

HAc (ml) HBr (ml) Time (min) Illumination

Recipe A 13 7 2:30 no

Recipe B 17 3 2:30 no

Recipe C 17 3 2:30 yes

Recipe C’ 17 3 15:00 yes

Recipe C’’ 17 3 180:00 yes

HAc:HBr solutions with variables: HBr concentration, etching time and illumination

• HBr concentration corresponds to 1.3 to 3.1 M

Etching recipes

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 5 of 10

HAc (ml) HBr (ml) Time (min) Illumination

Recipe A 13 7 2:30 no

Recipe B 17 3 2:30 no

Recipe C 17 3 2:30 yes

Recipe C’ 17 3 15:00 yes

Recipe C’’ 17 3 180:00 yes

Recipe A

Parameters: HAc (13 ml) : HBr (7 ml), 2:30 min

Etching results

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 6 of 10

Recipe A

Parameters: HAc (13 ml) : HBr (7 ml), 2:30 min

Etching results

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 6 of 10

M.I Schukfeh et al., Nanotechnology 25 (46), 2014

Etching results

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 6 of 10

Recipe B

Parameters: HAc (17 ml) : HBr (3 ml), 2:30 min

Etching results

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 6 of 10

Recipe B

Parameters: HAc (17 ml) : HBr (3 ml), 2:30 min

M.I Schukfeh et al., Nanotechnology 25 (46), 2014

Etching results

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 6 of 10

Recipe C

Parameters: HAc (13 ml) : HBr (7 ml), 2:30 min, illuminated

Etching results

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 6 of 10

Recipe C

Parameters: HAc (13 ml) : HBr (7 ml), 2:30 min, illuminated

M.I Schukfeh et al., Nanotechnology 25 (46), 2014

Etching results

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 6 of 10

Recipe C

Parameters: HAc (13 ml) : HBr (7 ml), 2:30 min, illuminated

M.I Schukfeh et al., Nanotechnology 25 (46), 2014

Etching results

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 6 of 10

Recipe C

Parameters: HAc (13 ml) : HBr (7 ml), 2:30 min, illuminated

M.I Schukfeh et al., Nanotechnology 25 (46), 2014

Etching results

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 6 of 10

Recipe C’

Parameters: HAc (13 ml) : HBr (7 ml), 15:00 min, illuminated

Etching results

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 6 of 10

M.I Schukfeh et al., Nanotechnology 25 (46), 2014

Recipe C’

Parameters: HAc (13 ml) : HBr (7 ml), 15:00 min, illuminated

Etching results

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 6 of 10

Recipe C’’

Parameters: HAc (13 ml) : HBr (7 ml), 180:00 min, illuminated

Etching results

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 6 of 10

Recipe C’’

Parameters: HAc (13 ml) : HBr (7 ml), 180:00 min, illuminated

Etching results

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 6 of 10

Prolonged etching results in a reduction of nanowire diameter from ~50 nm to ~25 nm

Recipe C’’

Parameters: HAc (13 ml) : HBr (7 ml), 180:00 min, illuminated

Etching of InP (InAs accordingly) with HBr proceeds in 2-step process:

Etching process

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 7 of 10

Etching of InP (InAs accordingly) with HBr proceeds in 2-step process:

1. Breaking up In/P and H/Br bonds and replacing them by In/Br and P/H bonds

Etching process

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 7 of 10

Etching of InP (InAs accordingly) with HBr proceeds in 2-step process:

1. Breaking up In/P and H/Br bonds and replacing them by In/Br and P/H bonds

Etching process

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 7 of 10

Etching of InP (InAs accordingly) with HBr proceeds in 2-step process:

1. Breaking up In/P and H/Br bonds and replacing them by In/Br and P/H bonds

2. Using more HBr units to form InBr3 and PH3

Etching process

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 7 of 10

Etching of InP (InAs accordingly) with HBr proceeds in 2-step process:

1. Breaking up In/P and H/Br bonds and replacing them by In/Br and P/H bonds

2. Using more HBr units to form InBr3 and PH3

Etching process

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 7 of 10

Etching of InP (InAs accordingly) with HBr proceeds in 2-step process:

1. Breaking up In/P and H/Br bonds and replacing them by In/Br and P/H bonds

2. Using more HBr units to form InBr3 and PH3

3. Impact of illumination?

Etching process

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 7 of 10

Etching of InP (InAs accordingly) with HBr proceeds in 2-step process:

1. Breaking up In/P and H/Br bonds and replacing them by In/Br and P/H bonds

2. Using more HBr units to form InBr3 and PH3

3. Impact of illumination?• Etching is facilitated by the presence of holes at the InP surface, needed for a

nucleophilic attack

Etching process

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 7 of 10

Etching of InP (InAs accordingly) with HBr proceeds in 2-step process:

1. Breaking up In/P and H/Br bonds and replacing them by In/Br and P/H bonds

2. Using more HBr units to form InBr3 and PH3

3. Impact of illumination?• Etching is facilitated by the presence of holes at the InP surface, needed for a

nucleophilic attack• Light generates electron / hole pairs

Etching process

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 7 of 10

Etching of InP (InAs accordingly) with HBr proceeds in 2-step process:

1. Breaking up In/P and H/Br bonds and replacing them by In/Br and P/H bonds

2. Using more HBr units to form InBr3 and PH3

3. Impact of illumination?• Etching is facilitated by the presence of holes at the InP surface, needed for a

nucleophilic attack• Light generates electron / hole pairs• Increased selectivity due to illumination not yet understood

Etching process

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 7 of 10

• Difference in kinetic etch constants for InAs and InP likely responsible for selectivity

Etching selectivity

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 8 of 10

• Difference in kinetic etch constants for InAs and InP likely responsible for selectivity

• May be related to thermodynamic quantities characterizing formation / breaking of bonds associated with the etching process

Etching selectivity

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 8 of 10

• Difference in kinetic etch constants for InAs and InP likely responsible for selectivity

• May be related to thermodynamic quantities characterizing formation / breaking of bonds associated with the etching process

Comparison of enthalpies of formation:

Etching selectivity

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 8 of 10

InAs AsH3 InP PH3

Standard enthalpy of formation [kJ/mol]

• Difference in kinetic etch constants for InAs and InP likely responsible for selectivity

• May be related to thermodynamic quantities characterizing formation / breaking of bonds associated with the etching process

Comparison of enthalpies of formation:

Etching selectivity

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 8 of 10

InAs AsH3 InP PH3

Standard enthalpy of formation [kJ/mol]

-58.8 66.4

• Difference in kinetic etch constants for InAs and InP likely responsible for selectivity

• May be related to thermodynamic quantities characterizing formation / breaking of bonds associated with the etching process

Comparison of enthalpies of formation:

Etching selectivity

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 8 of 10

InAs AsH3 InP PH3

Standard enthalpy of formation [kJ/mol]

-58.8 66.4

125.2 kJ/mol

• Difference in kinetic etch constants for InAs and InP likely responsible for selectivity

• May be related to thermodynamic quantities characterizing formation / breaking of bonds associated with the etching process

Comparison of enthalpies of formation:

Etching selectivity

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 8 of 10

InAs AsH3 InP PH3

Standard enthalpy of formation [kJ/mol]

-58.8 66.4 -61.3 5.4

125.2 kJ/mol

• Difference in kinetic etch constants for InAs and InP likely responsible for selectivity

• May be related to thermodynamic quantities characterizing formation / breaking of bonds associated with the etching process

Comparison of enthalpies of formation:

Etching selectivity

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 8 of 10

InAs AsH3 InP PH3

Standard enthalpy of formation [kJ/mol]

-58.8 66.4 -61.3 5.4

125.2 kJ/mol 66.7 kJ/mol

• Difference in kinetic etch constants for InAs and InP likely responsible for selectivity

• May be related to thermodynamic quantities characterizing formation / breaking of bonds associated with the etching process

Comparison of enthalpies of formation:

Etching selectivity

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 8 of 10

InAs AsH3 InP PH3

Standard enthalpy of formation [kJ/mol]

-58.8 66.4 -61.3 5.4

125.2 kJ/mol 66.7 kJ/mol

Over 45% less energy than InAs/AsH3

• Difference in kinetic etch constants for InAs and InP likely responsible for selectivity

• May be related to thermodynamic quantities characterizing formation / breaking of bonds associated with the etching process

Comparison of enthalpies of formation:

Etching selectivity

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 8 of 10

InAs AsH3 InP PH3

Standard enthalpy of formation [kJ/mol]

-58.8 66.4 -61.3 5.4

125.2 kJ/mol 66.7 kJ/mol

Over 45% less energy than InAs/AsH3

As a common product to both reactions, InBr3 was disregarded in the comparison

• A selective wet etching technique was developed to remove embedded nanoscale InP segments from InAs nanowires

Conclusion & Outlook

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 9 of 10

• A selective wet etching technique was developed to remove embedded nanoscale InP segments from InAs nanowires

• InP segments of 10 nm thickness in 50 nm diameter nanowires were successfully removed, yielding nanometer-spaced InAs electrodes

Conclusion & Outlook

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 9 of 10

• A selective wet etching technique was developed to remove embedded nanoscale InP segments from InAs nanowires

• InP segments of 10 nm thickness in 50 nm diameter nanowires were successfully removed, yielding nanometer-spaced InAs electrodes

• For prolonged etching, InAs nanowire diameter was reduced from 50 to 25 nm

Conclusion & Outlook

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 9 of 10

• A selective wet etching technique was developed to remove embedded nanoscale InP segments from InAs nanowires

• InP segments of 10 nm thickness in 50 nm diameter nanowires were successfully removed, yielding nanometer-spaced InAs electrodes

• For prolonged etching, InAs nanowire diameter was reduced from 50 to 25 nm

Future work:

Conclusion & Outlook

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 9 of 10

• A selective wet etching technique was developed to remove embedded nanoscale InP segments from InAs nanowires

• InP segments of 10 nm thickness in 50 nm diameter nanowires were successfully removed, yielding nanometer-spaced InAs electrodes

• For prolonged etching, InAs nanowire diameter was reduced from 50 to 25 nm

Future work:• Pushing towards removal of smaller (~5 nm) InP segments

Conclusion & Outlook

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 9 of 10

• A selective wet etching technique was developed to remove embedded nanoscale InP segments from InAs nanowires

• InP segments of 10 nm thickness in 50 nm diameter nanowires were successfully removed, yielding nanometer-spaced InAs electrodes

• For prolonged etching, InAs nanowire diameter was reduced from 50 to 25 nm

Future work:• Pushing towards removal of smaller (~5 nm) InP segments• Application in molecular electronics circuits

Conclusion & Outlook

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 9 of 10

• A selective wet etching technique was developed to remove embedded nanoscale InP segments from InAs nanowires

• InP segments of 10 nm thickness in 50 nm diameter nanowires were successfully removed, yielding nanometer-spaced InAs electrodes

• For prolonged etching, InAs nanowire diameter was reduced from 50 to 25 nm

Future work:• Pushing towards removal of smaller (~5 nm) InP segments• Application in molecular electronics circuits• Understanding role of illumination for enhanced selectivity

(InP/InAs)

Conclusion & Outlook

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 9 of 10

…for your attention.

Acknowledgments

Meinhard Schilling, EMG, TU Braunschweig, Germany

Frank Ludwig, EMG, TU Braunschweig, Germany

Partially funded by

Thank you…

Selective etching of InP in InAs/InP NWs | Schukfeh | IEEE Nano 2015 | 2015-07-30 | Slide 10 of 10