DOI: 10.5281/zenodo.16889713
title: InP(111) Etch-Track Orientation Statistics (n-type)

description: Overview

This dataset contains scanning electron microscopy (SEM) images of n-InP(111) after selective electrochemical etching, together with raw line-orientation measurements and derived plots (rose diagrams and intersection-angle histograms). The statistics quantify in-plane alignment of etch tracks, which reflects the crystallographic texture of the (111) surface—dominant ⟨110⟩ directions (and secondary ⟨112⟩)—and explain the large inter-family angles (~120–150°, typically ~135°).

 

Contents







 



InP111_orientation_dataset_v1/
  sem_images/                      # Raw SEM + instrument text exports (where available)
    obr6_InP_x5000SEI-1.bmp
    obr8_InP_x7000SEI.bmp
    obr8_InP_x6000SEI.bmp
    obr8_InP_x7000SEI.txt
    obr8_InP_x6000SEI.txt
  processed/                       # Analysis outputs
    angles_all.csv                 # Raw line azimuths (0–180°), length-weighted
    summary_per_image.csv          # Top peaks, peakness, modal intersection angle
    obr6_InP_x5000SEI-1_rose.png
    obr8_InP_x7000SEI_rose.png
    obr8_InP_x6000SEI_rose.png
    obr6_InP_x5000SEI-1_intersections.png
    obr8_InP_x7000SEI_intersections.png
    obr8_InP_x6000SEI_intersections.png
  metadata/
    sem_metadata_parsed.csv        # Parsed key:value items from JEOL text exports
    sem_metadata_raw.txt           # Raw JEOL text exports (verbatim)
  README.md                        # This file
  LICENSE.txt                      # CC BY 4.0 for data/figures; MIT for code (if added)
  CITATION.cff                     # Citation metadata



Data dictionary

processed/angles_all.csv





image_file: SEM filename the segment was extracted from




angle_deg: in-plane azimuth θ in degrees, reduced to 0–180° (axial data: lines have no arrow direction)




length_px: segment length in pixels (used as a weight in histograms)



processed/summary_per_image.csv





image_file: SEM filename




n_lines_detected: number of line segments used




top_azimuth_peaks: three tallest histogram bin centers (°) with normalized heights




peakness: ratio of the maximum bin to the mean bin (dimensionless)




intersection_modal_deg: modal acute angle (0–90°) between track families, from pairwise separations



Methods (abridged)

SEM images were converted to grayscale, contrast-equalized (CLAHE), edge-detected (Canny, σ≈2), skeletonized, and straight segments were extracted using the probabilistic Hough transform (minimum segment length ≈30 px; line gap ≈6 px; threshold ≈10).For each segment, the azimuth θ was computed relative to the image x-axis, reduced to 0–180° (axial data), and weighted by segment length. Length-weighted histograms (10° bins) and polar rose plots were generated. Acute intersection angles were computed as

ϕ=min⁡(∣θi−θj∣,  180∘−∣θi−θj∣),ϕ∈[0,90∘].\phi=\min\big(|\theta_i-\theta_j|,\; 180^\circ-|\theta_i-\theta_j|\big),\quad \phi\in[0,90^\circ].ϕ=min(∣θi−θj∣,180∘−∣θi−θj∣),ϕ∈[0,90∘].

Circular non-uniformity was assessed with the Rayleigh test for axial data (angles doubled into 0–360°). Very small p-values indicate privileged directions rather than a uniform distribution.

Software: Python 3.x; scikit-image, numpy, matplotlib. Scripts/notebooks can be supplied in a future minor release (v1.1).

Instrument metadata

JEOL text exports for two images are provided (sem_images/*.txt) and summarized in metadata/sem_metadata_parsed.csv. Typical settings: 10 kV accelerating voltage, SEI detector, WD ≈10 mm, magnifications 6000× and 7000×. Exact per-image values are in the text exports.

Provenance & limitations

Images originate from n-InP(111) after selective electrochemical etching in a multi-year research program. Representative fields were re-processed under a standardized pipeline to support orientation analysis. Pixel-based length weights are angle-invariant; if needed, lengths may be converted to µm using the pixel size or scale bar.

How to use





Excel/Origin: load angles_all.csv, filter by image_file, build a 0–180° histogram (10° bins); optionally plot in polar coordinates.



This research was funded by The National Research Fund of Ukraine with the support of the University of Cambridge, Great Britain, grant number 0124U000223 “Design and Research of Oxide Heterostructures for Portable Solar Cells”




image_file
n_lines_detected
top_azimuth_peaks
peakness
acute angle between top peaks




obr6_InP_x5000SEI-1.bmp
2494
135°, 45°, 35°
2.39
90°, 80°, 10°


obr8_InP_x7000SEI.bmp
266
165°, 45°, 105°
3.49
60°, 60°, 60°


obr8_InP_x6000SEI.bmp
310
165°, 45°, 105°
3.30
60°, 60°, 60°