Reproducing Li, Luo and Ye 2023: carbon across the SiO2/4H-SiC interface after a 1400 °C oxidation

One of the [studies we reproduced](/writing/interface-studies-reproduced) for [Questions we need Emily to answer](/writing/questions-for-emily-testing-a-theory-of-the-interface), the companion to [the essay](/writing/testing-a-theory-of-the-interface-with-an-ontology). Generated by `scripts/reproduce_studies.py` from `reproductions/li_2023.py`. Every value from the paper was read by an AI agent and has not been checked by a person; the sample and history were re-read from the PDF alone by a second agent that had not seen our earlier transcription.

The study and why we depend on it

S. Li, J. Luo and T. Ye, “Investigation of Reducing Interface State Density in 4H-SiC by Increasing Oxidation Rate”, Nanomaterials 13, 1568 (2023), doi:10.3390/nano13091568.

The one source in our library that measures composition across the SiC/oxide interface (challenge system 3, target composition profile). Figure 8 gives the carbon and oxygen atomic fractions from a STEM-EDS line scan across the interface for a sample oxidized dry at 1400 °C for 13 min and annealed in NO, with and without a phosphorus implant before oxidation. The paper also gives the oxide thickness of three samples (Figure 3) and interface state densities (Figure 6). The predictor has no program for a composition profile; this page records the profile, runs the thickness and interface-state programs on the stated history, and says what a carbon program would have to contain. A candidate carbon program, written in the language but not added to the predictor, is described in the alignment section.

How well can this study be reproduced?

Moderate for thickness, Low for the carbon profile. The oxidation itself is stated (dry O2, 1400 °C, 13 min) and so is the NO anneal (1200 °C, 70 min). Everything around them is not: the sacrificial oxidation, the field oxide, how a wafer entered and left a 1400 °C tube, the transfer to the NO anneal, the polysilicon deposition. The carbon profile (Figure 8) is an EDS line scan of a FIB lamella in arbitrary position units, with C at 0.36 in SiC where it should be 0.50; which samples it shows is inferred from the text. No program we hold predicts a composition profile, and the language cannot write the NO anneal or the implant.

The grade is ours and is about the paper as a source for simulation, not about the quality of the experiment: high means the sample, every step and its timing are stated well enough that a simulation needs no choices of ours; moderate that some choices are ours and are listed; low that the result depends on choices the paper does not constrain.

The sample and its history, played back

The sample is drawn from the simulation: layer heights and the read-outs are what the ISL programs compute at each moment of the history. Steps the language cannot state (a clean, a metallization, a measurement) are on the clock and marked as recorded, not simulated.

Does our sample and history match the paper's?

Left: the paper's own words, with the page of the PDF. Right: what we simulate. 7 same, 2 approximated, 3 assumed, 4 not in ours.

The timing of the history

Time is counted from the start of the first simulated step. A step the language cannot state takes no simulated time; where the paper gives its duration, the duration is in the last column. Stated means the paper gives the duration; partly stated that it gives a bound or a range; not stated; assumed that the duration in our history is ours.

OX

Simulated time in this history: 20 min.

Across the samples

Timing the paper does not give

• Sacrificial oxidation: temperature, time, gas, thickness.
• Field-oxide CVD and the implant: temperatures, and the time between them and the 1400 °C oxidation.
• How a wafer entered and left a 1400 °C tube: push, gas during push and pull, cooling.
• Transfer from the 1400 °C oxidation to the 1200 °C NO anneal; NO concentration; cooling after it.
• Polysilicon LPCVD temperature and time.
• No post-metallization anneal stated.

What the second reading changed

• There is no stored recipe or dataset for this paper (ontology/library.json: status skimmed, used by nothing). Everything here is from the second reading; nothing contradicts an earlier encoding because there is none.
• SOURCE.md says “carbon accumulation at the interface is reduced by the implantation” from the abstract. Figure 8 shows no carbon excess above the SiC level on either sample: the “accumulation” is a wider transition (3.6 against 2.7 nm, digitised), not a peak.
• SOURCE.md and the search notes give overlaps of about 6 and 3 nm; those are the paper's words. The digitised 90 to 10% carbon falls are 3.6 and 2.7 nm and the oxygen rises 3.5 and 2.8 nm, so the ratio is 1.3, not 2.
• The EDS fractions are not stoichiometric: carbon in SiC reads 0.36 (0.50 expected), oxygen in the oxide 0.61 (0.67), carbon in the oxide 0.03 (background). Only shapes and widths can be compared, not levels. Silicon is not plotted.
• The predictor's consumed-substrate ratio (0.46, STATUS hypothesis, “no source in our library states it”) is stated by this paper: 1:2.17, i.e. 0.461.

Their terms and ours

The simulation in our language

Each sample is one history file: a SAMPLE and a CONTROL_TRAJECTORY. This is the whole input; run it with PYTHONPATH=. python -m isl_harness.predict <file>.

OX

# OX
SAMPLE SiC_OX {
    FAMILY: SiC_SiO2
    ORIENTATION: 4H_SiC_Si_face
    OFFCUT_DEG: 4
    CLEAN: RCA
    DOPING: n_type_epi_5e15_to_1e16
}
CONTROL_TRAJECTORY History {
    EVENT Clean KIND clean TIMING assumed                        # RCA clean
    EVENT SacrificialOxide KIND other TIMING assumed             # Sacrificial oxide grown
    EVENT Strip KIND etch TIMING assumed                         # Native and sacrificial oxide removed in 10% HF
    EVENT FieldOxide KIND deposition TIMING assumed              # Field oxide by CVD
    RUN PushIn DURATION 120 TEMP 1000->1400 AMBIENT dry_O2 TIMING assumed VARY duration 10..900
    RUN Oxidation DURATION 780 TEMP 1400->1400 AMBIENT dry_O2 TIMING stated
    RUN Pull DURATION 300 TEMP 1400->900 AMBIENT dry_O2 TIMING assumed VARY duration 30..1800
    EVENT Deposit KIND deposition TIMING assumed                 # In-situ doped polysilicon gate by LPCVD
    EVENT Metal KIND metallization TIMING assumed                # Sputtered Al, 1 µm, front and back
    EVENT Measure KIND measurement TIMING assumed                # C-V and quasi-static C-V; FIB lamella, STEM-EDS line scan; SIMS
}

Low-imp-OX

# Low-imp-OX
SAMPLE SiC_Low_imp_OX {
    FAMILY: SiC_SiO2
    ORIENTATION: 4H_SiC_Si_face
    OFFCUT_DEG: 4
    CLEAN: RCA
    DOPING: n_type_epi_5e15_to_1e16
    IMPLANT_P: 30keV_1e12
}
CONTROL_TRAJECTORY History {
    EVENT Clean KIND clean TIMING assumed                        # RCA clean
    EVENT SacrificialOxide KIND other TIMING assumed             # Sacrificial oxide grown
    EVENT Strip KIND etch TIMING assumed                         # Native and sacrificial oxide removed in 10% HF
    EVENT FieldOxide KIND deposition TIMING assumed              # Field oxide by CVD
    EVENT Implant KIND other TIMING assumed                      # Phosphorus implant, 30 keV, 1e12 cm⁻²
    RUN PushIn DURATION 120 TEMP 1000->1400 AMBIENT dry_O2 TIMING assumed VARY duration 10..900
    RUN Oxidation DURATION 780 TEMP 1400->1400 AMBIENT dry_O2 TIMING stated
    RUN Pull DURATION 300 TEMP 1400->900 AMBIENT dry_O2 TIMING assumed VARY duration 30..1800
    EVENT Deposit KIND deposition TIMING assumed                 # In-situ doped polysilicon gate by LPCVD
    EVENT Metal KIND metallization TIMING assumed                # Sputtered Al, 1 µm, front and back
    EVENT Measure KIND measurement TIMING assumed                # C-V and quasi-static C-V; FIB lamella, STEM-EDS line scan; SIMS
}

High-imp-OX

# High-imp-OX
SAMPLE SiC_High_imp_OX {
    FAMILY: SiC_SiO2
    ORIENTATION: 4H_SiC_Si_face
    OFFCUT_DEG: 4
    CLEAN: RCA
    DOPING: n_type_epi_5e15_to_1e16
    IMPLANT_P: 30keV_1e13
}
CONTROL_TRAJECTORY History {
    EVENT Clean KIND clean TIMING assumed                        # RCA clean
    EVENT SacrificialOxide KIND other TIMING assumed             # Sacrificial oxide grown
    EVENT Strip KIND etch TIMING assumed                         # Native and sacrificial oxide removed in 10% HF
    EVENT FieldOxide KIND deposition TIMING assumed              # Field oxide by CVD
    EVENT Implant KIND other TIMING assumed                      # Phosphorus implant, 30 keV, 1e13 cm⁻²
    RUN PushIn DURATION 120 TEMP 1000->1400 AMBIENT dry_O2 TIMING assumed VARY duration 10..900
    RUN Oxidation DURATION 780 TEMP 1400->1400 AMBIENT dry_O2 TIMING stated
    RUN Pull DURATION 300 TEMP 1400->900 AMBIENT dry_O2 TIMING assumed VARY duration 30..1800
    EVENT Deposit KIND deposition TIMING assumed                 # In-situ doped polysilicon gate by LPCVD
    EVENT Metal KIND metallization TIMING assumed                # Sputtered Al, 1 µm, front and back
    EVENT Measure KIND measurement TIMING assumed                # C-V and quasi-static C-V; FIB lamella, STEM-EDS line scan; SIMS
}

OX-NO

# OX-NO
SAMPLE SiC_OX_NO {
    FAMILY: SiC_SiO2
    ORIENTATION: 4H_SiC_Si_face
    OFFCUT_DEG: 4
    CLEAN: RCA
    DOPING: n_type_epi_5e15_to_1e16
}
CONTROL_TRAJECTORY History {
    EVENT Clean KIND clean TIMING assumed                        # RCA clean
    EVENT SacrificialOxide KIND other TIMING assumed             # Sacrificial oxide grown
    EVENT Strip KIND etch TIMING assumed                         # Native and sacrificial oxide removed in 10% HF
    EVENT FieldOxide KIND deposition TIMING assumed              # Field oxide by CVD
    RUN PushIn DURATION 120 TEMP 1000->1400 AMBIENT dry_O2 TIMING assumed VARY duration 10..900
    RUN Oxidation DURATION 780 TEMP 1400->1400 AMBIENT dry_O2 TIMING stated
    RUN Pull DURATION 300 TEMP 1400->900 AMBIENT dry_O2 TIMING assumed VARY duration 30..1800
    EVENT NOanneal KIND other TIMING stated                      # Anneal in NO at 1200 °C, 70 min
    EVENT Deposit KIND deposition TIMING assumed                 # In-situ doped polysilicon gate by LPCVD
    EVENT Metal KIND metallization TIMING assumed                # Sputtered Al, 1 µm, front and back
    EVENT Measure KIND measurement TIMING assumed                # C-V and quasi-static C-V; FIB lamella, STEM-EDS line scan; SIMS
}

The sample “without pretreatment” of Figures 7 and 8 (PDF p. 8 names OX-NO and High-imp-OX-NO for the electron microscopy; Figure 8 does not name its samples).

High-imp-OX-NO

# High-imp-OX-NO
SAMPLE SiC_High_imp_OX_NO {
    FAMILY: SiC_SiO2
    ORIENTATION: 4H_SiC_Si_face
    OFFCUT_DEG: 4
    CLEAN: RCA
    DOPING: n_type_epi_5e15_to_1e16
    IMPLANT_P: 30keV_1e13
}
CONTROL_TRAJECTORY History {
    EVENT Clean KIND clean TIMING assumed                        # RCA clean
    EVENT SacrificialOxide KIND other TIMING assumed             # Sacrificial oxide grown
    EVENT Strip KIND etch TIMING assumed                         # Native and sacrificial oxide removed in 10% HF
    EVENT FieldOxide KIND deposition TIMING assumed              # Field oxide by CVD
    EVENT Implant KIND other TIMING assumed                      # Phosphorus implant, 30 keV, 1e13 cm⁻²
    RUN PushIn DURATION 120 TEMP 1000->1400 AMBIENT dry_O2 TIMING assumed VARY duration 10..900
    RUN Oxidation DURATION 780 TEMP 1400->1400 AMBIENT dry_O2 TIMING stated
    RUN Pull DURATION 300 TEMP 1400->900 AMBIENT dry_O2 TIMING assumed VARY duration 30..1800
    EVENT NOanneal KIND other TIMING stated                      # Anneal in NO at 1200 °C, 70 min
    EVENT Deposit KIND deposition TIMING assumed                 # In-situ doped polysilicon gate by LPCVD
    EVENT Metal KIND metallization TIMING assumed                # Sputtered Al, 1 µm, front and back
    EVENT Measure KIND measurement TIMING assumed                # C-V and quasi-static C-V; FIB lamella, STEM-EDS line scan; SIMS
}

The “pretreated sample” of Figures 7 and 8, by the same inference.

The programs the predictor ran on these histories: experiments/sic_interface_states/one_way_anneal.isl.template, experiments/song_sic/oxide_growth_sic.isl.template.

The model itself, experiments/song_sic/oxide_growth_sic.isl.template, as it is written. Every equation the simulation uses is in this text; the runtime holds no physics.

# ==============================================================================
# ISL MODEL: DRY THERMAL OXIDATION OF 4H-SiC (growth sector on a second material)
#
# The OPERATOR and OBSERVATION_MODEL blocks below are copied character for character
# from experiments/vitkavage_dit/oxide_growth.isl.template, the silicon program; a test
# checks that they are identical. Only the declared parameters differ.
#
# Song et al. (2004) fit their SiC data with the same linear-parabolic law, reading its
# two constants as including out-diffusion of the carbon product. The constants here are
# Arrhenius fits to that paper's Tables I and II, per crystal face
# (scripts/build_song_dataset.py). Nothing is fitted by us.
# Fields in {{braces}} are filled by scripts/run_song_sic.py.
# ==============================================================================
SAMPLE {sample_id} {{
    FAMILY: SiC_SiO2
    ORIENTATION: 4H_SiC_{face}_face
}}
STATE x_ox {{
    UNIT: cm
    INITIAL: x_i
    MIN: 0
    MAX: 1.0e-3
}}
CONTROL T {{ UNIT: K }}
CONTROL p_O2 {{ UNIT: atm }}
PARAMETER B0 {{ VALUE: {B0}; UNIT: cm^2 s^-1; STATUS: sourced; SOURCE: {source} }}
PARAMETER E_B {{ VALUE: {E_B}; UNIT: eV; STATUS: sourced; SOURCE: {source} }}
PARAMETER BA0 {{ VALUE: {BA0}; UNIT: cm s^-1; STATUS: sourced; SOURCE: {source} }}
PARAMETER E_BA {{ VALUE: {E_BA}; UNIT: eV; STATUS: sourced; SOURCE: {source} }}
# The constants above are already specific to the crystal face, so no further factor is applied.
PARAMETER r_or {{ VALUE: 1.0; UNIT: 1; STATUS: constant }}
# The paper sets the time offset to zero and reports a native oxide of about 2 angstrom.
PARAMETER x_i {{ VALUE: 2.0e-8; UNIT: cm; STATUS: sourced; SOURCE: Song et al., J. Appl. Phys. 95, 4953 (2004), native oxide about 2 angstrom, agent-read }}
PARAMETER p_ref {{ VALUE: 1.0; UNIT: atm; STATUS: constant }}
PARAMETER k_B {{ VALUE: 8.617333262e-5; UNIT: eV K^-1; STATUS: constant }}
CONTROL_TRAJECTORY {trajectory_id} {{
    RUN Oxidation DURATION {duration_s} TEMP {T_C}->{T_C} AMBIENT dry_O2
}}
# dx/dt = B / (2x + A), with A = B / (B/A).
OPERATOR F_LinearParabolicGrowth : OxideGrowth {{
    EQUATION: d(x_ox)/dt = (p_O2 / p_ref) * B0 * exp(-E_B / (k_B * T)) / (2 * x_ox + B0 * exp(-E_B / (k_B * T)) / (r_or * BA0 * exp(-E_BA / (k_B * T))))
}}
OBSERVATION_MODEL Obs_Oxide_Thickness {{
    TARGET: Thickness
    UNIT: cm
    EQUATION: Thickness = x_ox
}}
EVALUATION_CONTRACT {contract_id} {{
    FROZEN: true
    DATASET: data/derived/song_2004_sic_thickness.csv
    DATASET_DIGEST: sha256:{dataset_sha256}
    SPLIT: {split}
{targets}
}}

Our simulation against the paper

18 off, 4 not modelled of 22 numbers. Tolerance is stated per row; nothing was fitted for this page.

Aligning the simulation: what the unstated things would have to be

Every step whose timing or temperature the paper leaves open carries a range in the history above (VARY). scripts/align_study.py searched those ranges against the paper's numbers through the same predictor, first one unknown at a time, then all together. No parameter a program declares fitted was touched. The unknowns were chosen on OX only; every other number is a test they played no part in.

Together: PushIn duration 900 s (was 120); Pull duration 1800 s (was 300).

As reproduced: 0 of 22 within tolerance, median error 467.2%. Aligned: 3 of 22 within tolerance, median error 467.2%. On the held-out samples only: 0 of 18 within tolerance, median error 575.6% as reproduced, 2 of 18 within tolerance, median error 575.6% aligned.

Choices of program or material property, each scored on its own and on top of the aligned history:

What was searched. The paper states the 13 min at 1400 °C and nothing about getting the wafer into and out of the tube. Two unknowns, shared by all five samples: the time the wafer spends heating in oxygen as it enters (1000 to 1400 °C, 10 s to 15 min) and the time it spends cooling in oxygen as it leaves (1400 to 900 °C, 30 s to 30 min). They were chosen on OX alone (its thickness and three interface state densities); the other four samples are the test.

Only the thickness responds, and it wants both at their maximum. The interface-state program does not change with either time. The thickness is 37.8 nm as reproduced (−27% against 51.9 nm), 34.9 nm with 10 s in and 30 s out, 45.1 nm with 15 min in alone, 45.8 nm with 30 min out alone, and 52.4 nm (+1%) with both: the program needs about 25 min more in oxygen near 1400 °C than the paper's 13 min. Both values sit at the edge of their ranges, so the search does not establish a furnace cycle; the more likely reading is that Song's Si-face constants, extrapolated 250 °C above 1150 °C, grow too slowly at 1400 °C. Hijikata 2013 (p. 11) notes that near 1500 °C the faces oxidize alike, by another mechanism.

Scores. As reproduced 0 of 22 within tolerance (4 of them have no program); aligned 3 of 22. On the held-out samples 0 of 18, then 2 of 18: the implanted samples' thicknesses (52.7 and 53.5 nm) come within 1 and 2% of the aligned 52.4 nm. That tests nothing about the implant: the program predicts the same oxide for all three, and the measured effect of the implant (+1.5% and +3.1%) is smaller than the tolerance.

Interface states. The interface-state program (Kobayashi 2017's fit at 1150 and 1300 °C) gives 3.2, 2.3 and 1.6 × 10¹² cm⁻² eV⁻¹ at 0.3, 0.4 and 0.5 eV for every sample here. Against OX, the only sample with a history it can read, that is 62 to 75% high. The implanted samples are 4 to 8 times lower, the NO-annealed ones 7 to 10 times lower; no program has an implant or nitric oxide. Writing the NO anneal as argon at 1200 °C (variant) changes nothing: the one-way anneal's level at 1200 °C is above the as-oxidized level, so it removes nothing (0 of 22 alone, 3 of 22 with the aligned history).

With heating and cooling transitions. None of the four scenarios moves any number by more than 2%. Our history already ramps into the 1400 °C hold (the PushIn step), so the scenarios add no heat-up; their cooling continues from where our pull ends, 900 °C in oxygen, where the growth program adds well under 1 nm; and the interface-state program has no term that depends on the cooling.

No hydrogen step, so there is no Quantum ESPRESSO comparison on this page.

2 within, 12 off, 4 not modelled of 18 numbers with the aligned settings (the samples used to choose the unknowns are left out).

The carbon profile has no program, and a candidate shows why carbon in the oxide is not what Figure 8 measures. A program written in the language (sic_carbon_profile.isl, in the session's drafts, not added to the predictor) grows the oxide by the SiC growth law, emits a fraction ν_C of the carbon in the SiC consumed into the oxide at the interface (Hijikata's Si and C emission model, Eq. 10), lets it diffuse with Hijikata's D_C (Table 1: 3.8 × 10⁻¹¹ cm² s⁻¹ at 1400 °C), be oxidized inside the oxide at Hijikata's κ′ rates, and leave at the surface. The grid travels with the interface (FIELD, FLUX with upwind for the oxide carried away, BOUNDARY flux at the interface and the surface). With ν_C = 0.1 (Hijikata's Figure 6, Si face near 1100 °C; not measured at 1400 °C) it gives, at the end of the 13 min: 7.6 × 10¹⁵ C cm⁻² emitted, 99.9% of it out through the surface, 6.7 × 10¹² oxidized inside the oxide, 3.5 × 10¹² held; a carbon fraction of 1.8 × 10⁻⁵ on the oxide side of the interface (an upper bound: the grid's far end, 60 nm, stands in for a surface that is nearer while the oxide grows). After the 70 min at 1200 °C nothing is left (10⁻⁴⁴). The carbon crosses 52 nm of oxide in about a second. The result is linear in ν_C: even ν_C = 0.5 gives 9 × 10⁻⁵, 300 times below the EDS floor of 0.03. So the program predicts a step in carbon at the interface, the same for both samples, and the measured 3.6 and 2.7 nm widths must come from the SiC side of the interface, from roughness on the 4° off-cut, or from the probe and the lamella.

What a program must contain to predict Figure 8: (1) the moving SiC/SiO2 front, with a growth law that holds at 1400 °C; (2) carbon on the SiC side: emission into the SiC (Hijikata's Figure 2), the diffusivity of carbon interstitials in SiC and a term that holds carbon near the front (clusters, a transition layer; Hijikata's 1.5 nm interface layer). No source in our library gives these constants; (3) a term by which implant damage changes the front (an amorphized layer that oxidizes faster); (4) the NO anneal: nitrogen incorporation and carbon removal; (5) an observation that turns the fields into an EDS atomic fraction across a lamella: the profile convolved with the probe and projection width, plus the off-cut roughness; (6) a grid whose length follows the oxide thickness. Items 1, 2 and 4 are FIELD, FLUX and BOUNDARY statements the language has; 3, 5 and 6 are not writable today.

The thickness at 1400 °C needs constants that hold there; the alignment's 25 extra minutes in oxygen are a symptom, not a furnace cycle.

Predictor: the SiC program's consumed-substrate ratio (0.46, STATUS hypothesis, “no source in our library states it”) is stated here as 1:2.17 (0.461, p. 3). It can be relabelled sourced.

What our language and ontology cannot yet say

• Nitric oxide (and N2O, NH3) as gases. The NO anneal at 1200 °C for 70 min is a stated step the language cannot write; it is an EVENT here. mix:NO=1.0 would let it be simulated by a program that reads p_NO (nitrogen at the interface, Figure 9; the interface-state reduction, Figure 6).
• An implant statement. IMPLANT P ENERGY 30 keV DOSE 1e13 [THROUGH FieldOxide] as a history step, carrying the species, the projected range and the damage a program can read. The paper's central variable is a sample field no program reads.
• A profile observable with the instrument in it. The composition target has no observation form: an OBSERVATION_MODEL returns one number. A profile result (value against position from the interface) and a reduction such as convolve(F, w) with a stated probe width, sampled at positions, would let Figure 8 be scored and would separate the instrument from the interface.
• A grid whose length follows a state (the oxide thickness), so a surface sink sits at the surface while the oxide grows; today the candidate program's sink is at a fixed 60 nm and its carbon is an upper bound.
• OFFCUT read by programs. The 4° off-cut is recorded and ignored; it sets the step density that roughens the interface the EDS line crosses, and Song's constants are on axis.

With heating and cooling transitions

No paper we hold states how its wafers heated up or cooled down. The project owner specified scenarios for one Vitkavage wafer (isl_harness/vitkavage_transitions.py); isl_harness/thermal_transitions.py applies the same numbers to every sample here: a heat-up in nitrogen before the first furnace step (a hot push of 1 to 5 min, or a cold-furnace ramp of 60 to 120 min), the owner's radiative cooling knots after the last furnace step or after the paper's own pull (fast, or every time multiplied by 5), and ramps around an anneal at 300 to 500 °C. The paper's own steps are kept as written. All transitions are assumptions, written in the history with TIMING assumed.

The paper's own conclusions

What we would like Emily to check

1. Is Figure 8 the OX-NO and High-imp-OX-NO samples, as the TEM paragraph suggests?
2. How does one get a wafer into and out of a 1400 °C tube: pushed hot in oxygen, or loaded cold and ramped? How long is it above 1200 °C outside the 13 min?
3. What width would you expect from the probe and the lamella alone in a Themis Z EDS line scan across a 4° off-cut interface? Is a 3 nm 90 to 10% width at the instrument limit?
4. Was the implant through the CVD field oxide or into bare SiC in the gate window?
5. Is the 1:2.17 SiC-to-SiO2 thickness ratio a number you would accept as a sourced constant?